1. SEHI
Sheikh Technical Veterinary School (STVS)
Mapping of Rift valley fever
risk areas in Somaliland
A mini thesis submitted in a partial fulfilment for
requirements for the award of Diploma in Livestock
Health Sciences (DLH) of sheikh technical veterinary
school.
By: Osman Abdulahi Farah
Roll number: STVS/0087
Supervisor Dr. Ismail Kane
July 2011
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2. DECLARATION
I, Osman Abdulahi Farah declare that the work presented here is my original work, and has
not appeared anywhere else in any other form except for the references made from other
published works.
Students Name: ………………………………………………………………..
Signature: …………………………………………………………….................
Supervisor signature: …………………………………………………
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3. ACKNOWLEDGEMENT
In the name of Allah, the Most Gracious and the Most Merciful Alhamdulillah, all praises to
Allah for the strengths and His blessing in completing this thesis. Special appreciation goes to
my supervisor, Dr Ismail Kane, for his supervision and constant support. His invaluable help
of constructive comments and suggestions throughout the thesis works have contributed to
the success of this research. Not forgotten, my appreciation to my Tutor of information
technology Mr. Mohamed Aden Ahmed and Abdirahman Bare Dubad for their support and
knowledge regarding this topic.
I would like to express my appreciation to the Dean of studies in (STVS) Dr Abdulahi
Sheikh Mohamed Nour, H.O.D in STVS officer, Dr Ibrahim Osman Suleiman, principal of
STVS Dr. Thomas Bazarusanga, all my Tutors in STVS for their support during my
education in veterinary and STVS administration for their encouragements.
Sincere thanks to all my fellow students in STVS like Hassan Adam Hussein for his
technical support and my unforgettable class mates for their kindness and moral support
during my study.
Last but not least, my deepest gratitude goes to my beloved parents; Mr. Abdullah Farah
Xamse and Mrs. Zahra Mohamud Hussein and also to my sisters and brothers for their
endless love, prayers and encouragement.
CONTENTS PAGE NO
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4. Cover page…………………………………………………………………………………...1
Declaration------------------------------------------------------------------------------------------------2
Acknowledgement----------------------------------------------------------------------------------------3
Table of Contents-----------------------------------------------------------------------------------------4
CHAMPTER ONE INTRODUCTION AND LITERATURE REVIEW................................6
1.1 General Introduction ………………………………………………..………………….....6
1.2 Literature review of RFV disease……………………………………………………….....8
1.2.1 Disease definition…………………………………………………………………......9
1.2.2 A aetiology of the Rift Valley fever………………………………………………......9
1.2.3 Epidemiology of the Rift Valley Fever…………………………………….. ……......9
1.2.4 Pathogenesis………………………………………………………………………......9
1.2.5 Implication of human healthy………………………………………………………....9
1.2.6 Geographic distribution of Rift valley Fever………………………………………...10
1.2.7 Environmental conditions…………………………………………………………....11
1.2.8 Modes of transmission…………………………………………………………….....12
1.2.9 Clinical signs of Rift Valley fever…………………………………………………....13
1.2.9.1 Sheep and Cattle…………..…………………………………………………….…....14
1.2.9.2 Goat…………………………………………………………………….....................14
1.2.9.3 Human………………………………………………………………………...……...14
1.2.9.4 Camel………………………………………………………………………………...15
1.2.10 Pathology of RVF………………………………………………………………….....16
1.2.11 Diagnosis and Vaccination………………………………………………………...…17
1.2.12 Control………………………………………………………………….…………....18
1.2.13 Mapping of RFV disease……………………………………………………….........19
1.3. General and specific objectives……………………………………………………..…..19
1.3.1 General objectives……………………………………………………………………...19
1.3.2 Specific Objectives…………………………………………………………...…...........19
CHAPTER TWO METHOD AND MATERIAL....................................................................20
2.1 Data collection....................................................................................................................20
2.2 Data Management and Analysis.........................................................................................20
2.3 Administrative structure of Somaliland.............................................................................20
2.4 laboratory techniques.........................................................................................................22
2.5 Description of study of study area……………………………………………………….22
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5. 3.5.1 Climate geography……………………………………………………………………..23
CHAPTER THREE RESULTS.............................................................................................. 24
CHAPTER FOUR DISCUSSION...........................................................................................25
4.1discussion……………………………………………………………………………........25
CHAPTER FIVE CONCLUSION AND RECOMMEDATION............................................28
5.1 Conclusion………………………………………………………………………………..28
5.2 Recommendation…………………………………………………………………………28
ANNEX ONE REFERENCE ……………………………………………….…………........29
CHAPTER ONE: GENERAL INTRODUCTION AND LITERATURE REVIEW
1.1 introduction
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6. Rift Valley fever (RVF) is one of the most serious trans-boundary animal diseases. It is a
mosquito-borne viral disease, which causes periodic severe epidemics, principally involving
ruminant animals. RVF is also an important zoonosis and one of the significant acute
haemorrhagic fevers affecting human beings and animals (Shoemaker 2002).
The disease is most severe in sheep, cattle, goat, producing high mortality in newborn
animals and abortion in pregnant animals, it is a zoonosis and human become infected from
contact with tissue of infected animals or mosquito bite.(Shoemaker 2002).
RVF activity reported in 25 African countries (Meganand Bailey, 1989; Peters and Lin-thicum,
1994).The disease results in high mortality and abor-tions in domestic animals, and a
mortality rate of less than 1 percent among humans (Peters and Linthicum, 1994).
Rift Valley Fever was first recorded in South Africa in 1950-51 in the Northern Cape,
Western Free State and the then Southern Transvaal. It started in the Western Free State in
December 1950 and it continued until April 1951.
The first documented epizootic of RVF occurred on a farm in 1930-1931 near Lake
Naivasha, Kenya with high mortality among sheep (Daubney et al., 1931).The name Rift
Valley refers to the location of the first isolation of the virus in the Rift Valley region of
Kenya dominated by Savanna grasslands. Their findings showed that the disease was vector
borne, transmitted by a variety of mosquito species, and affected both domestic animals and
humans.
During 1977 ,epidemic occurred along the Nile delta and Valley in Egypt, causing an
unprecedented number of human infections and deaths, as well as numerous abortion in sheep
and goat and some loses in goats, and camels,
In September 2000, RVF broke out simultaneously in Jizan province in South West Arabian
ad joint Yemen (Shoemaker 2002)
A recent outbreak in Saudi Arabia and Yemen, (September through November 2000)
documents for the first time the occurrence of the RVF virus outside of continental Africa
(WHO, 2000). And as the main exporting country of livestock from Somalia, the first
suspected of this disease was Somalia as result of outbreak in yemen and Suadi Arabia
animals exported to Somalia was boycotted resulting overstocking and depreciation of
animal price contribute to household economy decrease.
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7. And the diseases come in to being in Somalia as a result of the events which coincided with
El-Niño in 1997 –1998 in the region. Targeted surveillance in sero-positive sites in central
and south Somalia was carried out by the Somali component of the PACE project in 2004.
Following the massive RVF epizootic in north-eastern Kenya in 2006 – 2007, around a 100
human cases were suspected and one confirmed in southern Somalia (WHO/CDC), in parallel
with reports of high abortion rates in the small ruminants. As from January 2007, a targeted
survey was initiated in the Afmadow District (South) SAHSP (Somali Animal Health Service
Project 2007) .
The outbreaks were confined to north-eastern Kenya and the southern regions of Somalia and
no cases were reported in northern Somalia (FAO, 1998; WHO, 1998). However, considering
the frequent movement of livestock from south and central Somalia to the north (and from
Puntland to Somaliland) for export, the risk is considerable enough for importing countries to
suspect the presence of RVF in Somaliland and Puntland where animals are shipped and for
authorities of these States to carry out surveillance activities.
However, the application of statistically valid methods in Somalia is difficult due to the
pastoral nomadic context. The high mobility of livestock and the lack of a suitable sampling
frame for the lower administrative divisions make it nearly impossible to apply rigorous
random sampling methods.
Screening in Somaliland in 2001 and in Puntland in 2003 which targeted mainly sheep and
goats aged 1–2 years (97% of surveyed animals) revealed no signs compatible with the
disease but an overall sero-prevalence of 2 _ 0.02% (90/4570) and 5 _ 0.3% (206/4050),
respectively, Although results of the screening in Somaliland 2001 showed infection
prevalence in most region (five to six) the number of positives herds were concentrated in
Sanaag, Togdheer, and Sool region located within the Nugal Valley with a herd of prevalence
of 21 to 22 and (30%), this compared to 9 and 12% in Hargeisa and Sahil Regions.
this survey (GIS) software (Arcview1) was used to generate at random the required number
of sites within the area where sampling needs to take place, be it at zone, country, region or
even district level.As result of limited studies of rift valley fever in Somaliland this study was
aimed to show risk areas in Somaliland by using Arc GIS software version 9.3.1.
LITERATURE REVIEW
1.2.1 Definition of the disease
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8. Rift Valley fever (RVF) is acute or per acute disease of domestic ruminants in Africa and
Madagascar, caused by a mosquito- borne virus and characterized by fever, abortion, necrotic
hepatitis and haemorrhages, high mortality in young animals but infection are frequently in
apparent or mild,
1.2.2 Aetiology of RVF
RVFV has morphological and physiological properties typically of a member of the
phlebovirus of the Family Bunyaviriadae (Woods 2002).
A host cell derived bi-lipid- layer enveloped through which virus coded glycoprotein
composed of the three RNA segments, L(large),M(medium ),S(small )it contained in a
separate nucleocapsid within the viron , R FV is an enveloped virus with a diameter of 80 to
120 mm.
RVFV, which attaches to receptors on susceptible cells, it internalised by endocytosis and
replication occur in the cytoplasm by budding through endoplasmic reticulum in the Golgi
region (Struthers, & swanepoel 1982).
The virus can be grown in and readily produce cytopathic effect and plaque in virtually all
common continuous line and primary, including Primary calf and lamb kidney or tests cells,
the only exception s being primary macrophages and lymphoblastoid cell lines (Peter, 1981).
1.2.3 Epidemiology of the RVF
RVF is widespread in African and serious outbreaks have been encountered in both animals
and man in Egypt, Sudan, Kenya, South Africa, Zimbabwe, Zambia, and Senegal (Peters,
1981).
Over the last 40 years, numerous RVF outbreaks have occurred in most countries of sub-
Saharan Africa as well as Madagascar and Egypt (Meegan 1981, Zeller et al. 1997, House et
al. 1992).
Many of these outbreaks have been devastating to farming economies due to the associated
livestock losses and prohibited trade. In September 2000, RVF cases were confirmed in Saudi
Arabia and Yemen, marking the first reported occurrence of the disease outside the African
continent.
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9. This outbreak raised concerns that RVF virus may continue to spread to areas with a variety
of ecological conditions that were previously uninfected with the virus (Jupp et al. 2002,
Anyamba et al. 2006, Bird et al. 2007, Evans et al. 2007, WHO 2007b).
1.2.4 Pathogenesis of the RVF
After injection of the virus in tissue, initial replication occur at the site of infection followed
by viraemia and localisation of the virus in the target organs especially the liver, spleen and
kidneys. Further, replication of the virus in these organs amplifies the viraemia, severe
destruction of the hepatic cells, which is caused by the cytopathic effects for the virus (Peter,
1981).
Damage to the blood vessel walls causes vasculitis and widespread haemorrhages in the
affected tissue (Maar & Genfand 1979).
1.2.5 Implication of human healthy
human become infected from contact with infected tissue or from mosquito bite , in contrast
to the main vectors in the Egypt epidemic of 1977- 78 in south Africa people become infected
in contract with animals tissue , for instance where no such history can be obtained an it must
assumed that infection has resulted from mosquito bite.(Chambers, and warepoel. 1980)
Generally, person s who become affected are involve in livestock industry such farmers, who
assist in dystocia of livestock , farm labourers, who salvage carcasses for human consumption
,veterinarian and their assistants, and abattoir workers .( Maar & Genfand 1979)
Many reports of human becoming infected with RVF while, investigating the disease in the
field or laboratory. (Findlay, 1932)
Moreover, highest infection rates were found in workers in the by-product section of abattoir
in Zimbabwe Human infection results from infected virus with abraded skin, wound or mucus
membrane in the field during Egypt epidemic. (Brown 1981)The first known human fatality
was recorded in 1943 in laboratory worker in the USA soon after the initial isolation of the
virus (Schweitzer and Rivers, 1934), since the infection was complicated by thrombophlebitis
and patient died from pulmonary embolism.
1.2.6 Geographic Distributions
9

10. Since the first major outbreak of RVF was recorded close to Lake Naivasha in Kenya in
1930-1931 (Daubney et al. 1931, CDC 2004b), RVF outbreaks in Africa have occurred as far
north as Egypt, throughout most of sub-Saharan Africa and as far south as Southern Africa
(House et al. 1992, Davies and Martin 2003). One of the most notable epizootics of RVF
occurred in Kenya in 1950-1951 and resulted in the death of an estimated 100,000 sheep
(CDC 2004b). The 1977 RVF outbreak in Egypt resulted in both animal and human cases
and it was believed to have started due to the importation of RVF virus infected domestic
animals from Sudan (Gad et al. 1986, Peters and Linthicum 1994). In 1987 transmission of
the RVF virus to humans in West Africa (Senegal, Mauritania) was linked to the altered
interactions between humans and mosquitoes that resulted from flooding of the lower Senegal
River during construction of the Senegal River dam project (CDC 2004b).
In 1997- 1998 a RVF outbreak in East Africa affected 89,000 people and caused over 400
deaths (Gerdes 2004). A severe form of the disease was seen in Mauritania (1998) where
many thousands of people became sick, 200 people died, and abortion losses in livestock
were heavy (CDC 2004b, Gerdes 2004).
The 2000 outbreak in Saudi Arabia and Yemen was particularly alarming as this was the first
time RVF virus was detected outside the African and created mosquito-breeding habitats. In
just four months, 155 people had died, and the outbreak had forced the closure of livestock
markets in Kenya devastating the economy of the region (CDC 2007).
From November 2006 through March 2007 RVF outbreaks occurred in Somalia, Tanzania,
Sudan, and Kenya (ProMed Mail 2007). In Kenya alone, there were 684 human cases with
155 deaths (Linthicum et al. 2008).
The most recent cases of clinical disease or infection (without clinical disease) involving
domestic ruminant livestock and humans have occurred in Madagascar, South Africa, and
Sudan (WHO 2008, OIE 2008, Kasari et al. 200
1.2.7 Environmental Conditions
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11. The role of environmental elements in the epidemiology of vector-borne diseases such as
RVF is well known. Environmental elements such as climate (e.g., temperature, humidity,
annual rainfall, intensity of rainfall), hydrology (e.g., proximity to lake/dam, irrigation,
accumulated water, proximity to river), and topography (e.g., elevation, land- cover)
influence vectorial capacity (House et al. 1992, Chevalier et al. 2004a, Turell et al. 2005,
Clements et al. 2006). To have high vectorial capacity, which in turn increases the
probability of contact between hosts and vectors and the likeliness of RVF virus
establishment and spread, competent vectors must be in an environment suitable for vector
bioecology (e.g., population dynamics and biting activity ) and virus transmission (Turell et
al. 2005).
Environmental conditions can affect the ability of mosquitoes to transmit arboviruses such as
RVF virus. For instance, the extrinsic incubation (EI) period (the time interval between
ingestion of the virus and subsequent transmission by the mosquito) of RVF virus depends on
ambient temperature (Brubaker and Turell 1998, Turell et al. 1985, Turell 1989, House et al.
1992, Diallo et al. 2005). In general, studies have consistently shown that the EI period is
inversely related to temperature (Turell et al. 1985). However, the magnitude of the effect of
temperature on both infection and transmission rates appears to vary for different virus-mosquito
combinations (Turell et al. 1s985).
Changes in climate (e.g., humidity, rainfall, and temperature) can alter the geographic ranges
and life cycles of plants, animals, insects, bacteria, and viruses (Longstreth and Wiseman
1989).
Climate changes conducive to vector bioecology in habitats frequented by host species could
result in vector population growth and increased disease transmission (Longstreth and
Wiseman 1989).
1.2.8 Modes of Transmission
11

12. The mode of RVF virus transmission may be vector-borne, airborne or from direct contact
with body fluids of infected animals. May transmit the RVF virus mechanically (Hoch et al.
1985, House et al. 1992, Davies and Martin 2003), mosquitoes are the main RVF vectors
transmitting the virus to animals and humans (Meegan and Bailey 1988).
Many mosquitoes (e.g., Aedes, Anopheles, Culex, Eretmapodites, and Mansonia), transmit
the RVF virus and are infected naturally (Turell and Bailey 1987, Turell et al. 1990, Traore-
Lamizana et al. 2001, Chevalier et al. 2004a).
RVF virus is most often transmitted to humans by Aedes and Culex species of mosquitoes
(Linthicum et al. 1999, CDC 2004b).
Transmission of RVF virus to people working with livestock (e.g., when slaughtering or
handling infected animals or touching contaminated meat during the preparation of food or in
laboratory facilities) has frequently been an indicator of epizootic RVF virus activity (Davies
and Martin 2003). Infection through aerosol transmission of RVF virus has resulted from
contact with laboratory specimens containing the virus (Davies and Martin 2003, CDC
2004b), however, there have been no recorded direct human-to-human transmission of RVF
virus to date (Kasari et al. 2008).
RVF virus is maintained in the eggs of female floodwater Aedes mosquitoes, which breed in
isolated grassland depressions called dambos (Linthicum et al. 1985). The eggs are capable
of surviving in dry soil until the next heavy rainfall floods the dambos producing favourable
conditions for the eggs to hatch. Subsequently, very large numbers of adult mosquitoes
emerge (Linthicum et al. 1984; Davies et al. 1985, Ba et al. 2005, Anyamba et al. 2006) and,
if infected, transfer the RVF virus to livestock and other animals on which they feed. These
vertebrate blood meal hosts may become infected and develop a viremia (Linthicum et al.
1985, Evans et al. 2007). RVF epizootic periods result when waters persist a month or more
past the emergence of Aedes mosquitoes.
Secondary vector species (e.g., Culex spp.) to breed, generate large populations, feed on
animals with high levels of viremia (Linthicum et al. 1985, Davis and Martin 2003, Chevalier
et al. 2004a, Evans et al. 2007), and subsequently spread infection to animals beyond the area
of the original outbreaks (Linthicum et al. 1999, Anyamba et al. 2001, Woods 2002, CDC
2004b). Cattle and sheep are the primary amplifiers of the disease (Meegan and Bailey 1988,
Longstreth and Wiseman 1989, Kasari et al. 2008). It has also been suggested that reservoir
animals (RVF infected rodents or wild ruminants) may be affecting domestic animals in
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13. shared grasslands, and thus, maintain the virus during inter-epizootic periods. Sylvatic
(wildlife-mosquito) cycling of RVF virus could maintain the virus at low levels and enable
transmission of the virus from wildlife to wildlife and occasionally to livestock (Evans et al.
2007). Although Evans et al. 2007 found that African wild ruminants do become infected
with RVF virus,
Figure1, Rift valley fever virus transmission cycle (from Davies and Martin 2003).
1.2.9 Clinical sign of RVF
RVF virus is a zoonotic pathogen endemic to Africa (Peters and Linthicum 1994).
The susceptibility to and severity of RVF virus infection in numerous vertebrates (e.g., cattle,
sheep, goats, camels, rodents, wild ruminants, buffaloes, and antelopes, ) has been
determined during epizootics and in laboratory studies. Although RVF virus infects a wide
range of hosts, including humans, the most significant infections occur in domestic livestock
(e.g., sheep, cattle, goats, camels, and buffalo)
1.2.9.1 Sheep and Cattle
The most important animal species in RVF epidemics are sheep and cattle. Both sheep and
cattle suffer significant mortality (e.g., greater than 90% in lambs and calves less than one
13

14. week of age) and abortion (virtually 100%) after infection, and they become sufficiently
viremic to infect many arthropod vector species (Peters and Linthicum 1994, House et al.
1992, EFSA 2005).
Sheep are extremely susceptible to RVF virus.
Onset is marked by high fever (40-42oC). Significant clinical features in affected lambs, kids,
and adult sheep also include listlessness, weakness, anorexia, rapid respiration, excessive
salivation, vomiting, fetid diarrhoea, and abortion (Daubney et al. 1931, House et al. 1992).
In older lambs and adults, the incubation period is between 24 and 72 hours, and the mortality
rate is 20-30% (House et al. 1992). The most severe reactions occur in newborn lambs and
kids, which die within hours of infection, rarely surviving more than 36 hours (Linthicum et
al. 2008).
Cattle Adult cattle exhibit clinical signs of disease infrequently, but some may develop acute
disease with clinical features similar to those of sheep. Frequently abortion is the only
manifestation in this species. The mortality rate in native adult non-pregnant cattle does not
usually exceed 10 percent (House et al. 1992). are less severely affected with RVF than
sheep.
The mortality rates in calves are generally lower than in lambs and vary widely (20-70%)
between outbreaks (Peters and Linthicum 1994, House et al. 1992, OIE 2008).
1.2.9.2 Goats
Goats are generally less severely affected than sheep (e.g., 1977-78 Egyptian outbreaks),
with much lower morbidity and mortality, fewer abortions, and less severe clinical signs
(Imam et al. 1979, Davies and Martin 2003). Abortion in goats and mortality in kids were
recorded in Kenya in 1930, the Sudan in 1973, South Africa and Namibia in 1974-75, and in
West Africa in 1987 (EFSA 2005). Older kids and goats may develop in apparent, per acute
or acute disease (OIE 2008).
1.2.9.3 Camels
Camels do not normally show any clinical signs of RVF infection, however, antibodies to
RVFV have been detected in camels and RVF virus has been isolated from then during
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15. epidemics, As in cattle and sheep, high abortion rate (100%) is a common consequence of the
infection in pregnant animals and neonatal mortality may occur in camel foals born during
RVF epizootic periods (Davies and Martin 2003)
in Senegal and South Africa (Gora et al. 2000, Chevalier et al. 2004a). Nevertheless, several
studies have suggested that rodents play no role in natural outbreaks of RVF in Africa
(Davies 1975, Swanepoel et al. 1978, EFSA 2005).
In addition, Poultry and wild birds are not susceptible to RVF virus (Davies and Martin
2003).
1.2.9.4 Humans
Humans with RVF typically have either no symptoms or mild Influenza-like illness with
fever, generalized weakness, muscle and joint pain, dizziness, photophobia, anorexia, and
sometimes nausea and vomiting (Davis and Martin 2003, CDC 2004b). Recovery usually
occurs within 4-7 days, however, in some cases the disease progresses to ocular disease.
Other, often fatal, complications include hemorrhagic fever and encephalitis (which can lead
to headaches, coma, or seizures). In humans the case mortality rate is generally low
(approximately 1%), but full recovery may be protracted and long-term ocular and
neurological complications have been reported (FAO 2008). However, in some cases
mortality can be as high as approximately 25% when proper public health interventions are
not undertaken during an epidemic/epizootic as was the case in Sudan in 2007 (WHO 2007b).
1.2.10 Pathology of Rift Valley Fever
The hepatic lesions of RVF are essentially similar in all domestic animals and humans,
varying with the age of the affected individual. (Coetzer. 1977) In most severe lesions occur
15

16. in aborted sheep foetuses and new born- lambs in which the liver is usually moderately to
greatly enlarged , soft, friable and yellowish-born to dark reddish –brown in colour with
irregular congested patches and some lines haemorrhages of varying size scattered
throughout the parenchyma (Easterday,B.C.,1963)
Hepatic lesions in new- born lambs are almost invariably accompanied by numerous
petechiae and ecchymoses in the mucosa of the abomasums and its content are dark chocolate
–brown as result of the presence of partially digested blood.
Most mature sheep and cattle the spleen is slightly to moderately enlarged, with
haemorrhages in the capsule. Sometimes in Adult sheep edges of the spleen becomes dark-blue-
ish –red, circumscribed areas, 10 to 20 mm in diameter. (Coetzer, J.A.W and Mesi, G.d.
1975)
Lesions in newborn lambs are pyknosis and karyorrhexis of lypmnodes in lymphoid tissue,
cloudy swelling and hypotropic degeneration of the epithelial cells of the convoluted tubules
of the kidney and necrosis of the some cellular element in the glomeruli in ten per cent of
lambs, multifocal necrosis and haemorrhages in the adrenal cortex (Coetzer 1977).
Many animals have lung congestion, alveolar and interstitial oedema, haemorrhages, a few
fibrin thrombi in alveolar walls, emphysema, scattered neurophils infiltration and necrosis of
interlobular septa and peri-bronchial lymphoid tissue. (In human encephalitis is characterized
by focal necrosis with leukocyte infiltration and perivascular cuffing)(Van ders.1985).
1.2.11 Diagnosis and Vaccination
The mild influenza-like symptoms in single human cases of RVF can be confused with many
viral diseases. However, a RVF epizootic outbreak should be suspected if there is a sudden
and widespread onset of many abortions in domestic animals, high neonatal mortality and
16

17. acute febrile disease with the presence of liver lesions. Cases of disease in people associated
with the affected animals also assist in making a tentative RVF diagnosis. Climatic and
ecological factors such as the presence of high mosquito populations and/or flooding of
grassland depressions can contribute to provisional RVF diagnoses (Davies and Martin
2003).
There are two types of laboratory tests used to confirm provisional RVF diagnoses. The first
is to identify or isolate the RVF virus or antigen. For example, the virus can be isolated via
intraperitoneal inoculated mice or hamsters, immunofluorescent or peroxidase staining of
tissue culture, simple agar gel immune diffusion tests using liver or spleen tissue, and
immune sera RT-PCR (reverse transcription-polymerase chain reaction) (Davies and Martin
2003, OIE 2008).
The second method to confirm provisional RVF diagnoses is to detect specific antibody to the
RVF virus. The presence of RVF specific antibody or IgM can be demonstrated with
enzyme-linked-immunosorbent serologic assay (ELISA), microtiter virus-serum
neutralization tests in tissue culture, or plaque reduction tests in tissue culture (Davies and
Martin 2003, OIE 2008).
No specific treatment exists for Rift Valley fever, In most humans RVF cases, symptoms are
mild and are managed with supportive therapy. Both inactivated and live-attenuated vaccines
have been developed to help control RVF outbreaks (House et al. 1992). Routine vaccination
of non-pregnant livestock in Africa is recommended prior to outbreaks, but has been
prohibitively expensive, leading to endemicity of RVF in most African countries (Balkhy et
al. 2003, Davies and Martin 2003, OIE 2008). No vaccine is currently licensed or
commercially available for humans or livestock in the United States (WHO 2007b, Britch et
al. 2007).
1.2.12 Control
Control of vectors and host movements is necessary to interrupt the epidemiological cycle of
RVF virus and thereby lessen the potential impact of an outbreak by lowering disease
transmission rates. Effective vector control methods include hormonal inhibitors such as
methoprene, widespread use of vehicle or aerial mounted insecticide sprays targeting adult
17

18. mosquito species, and strategic treatment of mosquito breeding habitats and soils with
larvicides and insecticides, respectively (Davies and Martin 2003).
Since viremic host animals could arrive in an uninfected country within the incubation
period, movement of animals for trade from enzootic/epizootic areas should be banned during
RVF epizootic periods (Davies and Martin 2003). Also important in controlling disease
spread to and among humans is public education to discourage practices that promote
transmission. This includes educating the public to avoid direct contact with the blood and
body fluids of sick or dead animals unless appropriate levels of personal protection are used
and to use personal protection against mosquito bites (e.g., long-sleeved shirts and pants and
mosquito repellent).
1.2.13 Mapping of the RVF
A GIS is a computer-based system that combines digital geo-referenced (spatially- related)
and descriptive data for mapping and analysis (Brooker et al. 2002, Connor et al. 1995). One
of the main strengths of a GIS is its ability to integrate different types of spatial and non-spatial
data (Brooker et al. 2002).some examples of the types of data overlaid and analyzed
using GIS are population data (e.g., census, socio-economic, and animal population data),
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19. land-use and public infrastructure data, transportation networks data (e.g., roads and
railways), health infrastructure and epidemiological data (e.g., data on mortality, morbidity,
disease distribution and healthcare facilities), and environmental and ecological data
(e.g.,climate and vegetation data) (Kamel et al. 2001).
GIS technology can be used to manage and monitor different aspects of disease, from
incident tracking to epidemiologic analysis and assessment of risks (Allen and Wong 2006).
For example, a GIS can be used to map available epidemiological information and relate it to
factors known to influence the distribution of infectious diseases, such as climate and other
environmental factors that affect vector bioecology (Brooker et al. 2002, Allen and Wong
2006).
1.3 GENERALAND SPECIFIC OBJECTIVES
1.3.1 GENERAL OBJECTIVES
The general objectives of this mini thesis are to show areas of risk of rift valley fever in
Somaliland regions.
1.3.2 SPECIFIC OBJECTIVES
To indicate high-risk areas in Somaliland regions by using ArcGIS software
To estimate prevalence of surveyed four regions in Somaliland.
CHAPTER TWO MATERIALS AND METHODS
2.1 Data Collection
The input of data was obtained from SAHSP office in Hargeisa, where relevant information
was expected to be available like Ministry of livestock. In addition, data were selected in
survey of four regions in Somaliland where ArcGIS software /Stata IC 11.0 was used.
19

20. 2.2 Data Management and Analysis
Data from SAHSP were managed and entered into databases by using ArcGIS version 9.13
(Brooker) 2002, (Connor et al. 1995) due to short time of study. For the statistical analysis
the software Stata IC/11 was used to carry out exploratory analysis of potential RVF Also
were used data input of excel Microsoft programme.
2.3 Administrative structure of Somaliland
The Somaliland administrative structure has frequently been subject to Modification, to this
serological study of mapping RVF there are 4 regions composed of (12) districts. Each region
composed 30 locations and out of this four regions were selected where 900 samples were
extracted and the animals bleed were Sheep and Goat in those four regions. But Age group
were different according sheep and goat.
Table 1: Structure of the different administrative levels of sampling
Included in the
above
administrative
level
Region
District Location Sites
Total 4 12 30 900
Mode - 164 30 313
Average 225 75 30 331
Range 198 134 5 38
Table 2: List of relevant variables included in the database along with the number of
observations available
Variable
Number of samples
for which it was
recorded
% of samples for
which it was
recorded
20

21. Localization
Region
900 100%
District
900 100%
Location
900 100%
Site
900 100%
Species
Goat
456 51%
Sheep
444 49%
Age
1-5
Sex
Male
356 40%
Female
544 60%
Map2. Shows sampling location
21

22. 2.4 Laboratory techniques
Field collection samples during the survey of serological investigation samples were sent to
Nairobi laboratory were used IgG antibodies of ELISA to confirm the presence of RVF Virus
surveyed regions in Somaliland.
2.5 Description of the Study area
The republic of Somaliland is located in the Horn of Africa. Its boundaries are defined by the
Gulf of Aden to the north, Somalia in the east, Ethiopia in the South West, and in the
northwest. It lies between the 08°00' – 11°30' parallel north of the equator and between
42°30' – 49°00' meridian east of Greenwich. The capital of Republic of Somaliland is the city
of Hargeisa (elevation 1347 meters) but the country has a total area of 137,600 km2 with
coastline that extends about 850km along the southern African shores of the Gulf of Aden
however, The population of the Somaliland is about 3.5 million,
The country is divided into six regions namely; Maroodi jex, Awdal, Sahil, Togdheer, Sool
and Sanaag that are sub divided into 33 districts.
22

23. Figure2 shows map of study area
2.5.1 Climate and Geography
Somaliland is situating between 8o and 12o north of the equator. Climatically the country has
semi arid warm weather, where the daily average temperature ranges from 25o to 35Co.
The country’s three distinguish topographical features are the GUBAN, or the hot arid coastal
plains; the rolling highland of the Oogo which also contains some rugged and inaccessible
mountain ranges and Hawd plateau which stretches well into Ethiopian territory Southwards.
The coastal plain Oogo is very hot, with maximum temperature balanced around 30oC
throughout the year, reaching 40oC-45oC between May and September. Rainfall is generally
scarce, and vegetation is sparse. Somaliland is characterized by its great variations in
topography, climate and population. The four distinct seasons are: two main rainy seasons
known as “GU “or spring from April to June and short season “Deyr”or autumn rainy period
from September to November and two dry seasons of” Hagaa” or summer form July to
August and then long dry, cold “Jilaal”or winter from December to March.
23

24. CHAPTER THREE RESULT
Table 1: Prevalence of Rift Valley in the four surveyed regions
Regions
Number of samples
collected in each region and
% of the whole
survey
Prevalence with 95%
Confidence Intervals
Marodi jex 60 (7%) 0.15 (0.05-0.25)
Sanaag 318 (35%) 0.116352201 (0.11-0.15)
Sool 270 (30%) 0.185185 (0.18-0.25)
Togdheer 252 (28%) 0.107142827 (0.10-0.14)
Total 900 (100%) 0.137 (0.13-0.15)
Map1 of Rift Valley Survey Result
Map2 shows Rift Valley Risk sites serological status
24

25. Map3 shows Somaliland Digital Elevation Model (DEM)
Map 4 shows Somaliland Rift Valley Risk Areas
25

26. CHAPER FOUR DISCUSSION
4.1 Discussion
As one way of extracting information, desk review has been used due to the short time frame
of the study period. Therefore, an already stored data has been received from SAHSP
regional office through Dr. Ismail Kane with permission from Ministry of livestock. And the
data was analyzed in ArcGIS view programme to identify the high risk areas for rift valley
fever in Somaliland regions.
As recommended by James (1998) and applied by Terra Nuova in a previous surveys in
Somaliland and Puntland, and to overcome the lack of sampling frame due to high mobility
of animals which encompasses as one of the pastoral nature of the communities surveyed,
GIS system has been sorted out as the only method to help us achieve our objective to I
identify the high risk areas in Somaliland.
Over all sero-prevalence of this study was (14%) which is high according to previous reports
in Somaliland (Berkvens 2001) and in punt-land 2003 has prevalence of (5%) because in
2001 rainfall was not so much compared to 2002 – 2004 that is why carrier vectors highly
spread of RVF virus in those animals which are susceptible to the disease.
However, the comparison made between four surveyed regions risk areas of rift valley fever
in Somaliland are Sool and Marodi jex as show on Map 5 compared to Sanaag and Togdheer
and this is in agreement with previous studies conducted by Terra Nuova with help of
Ministry of livestock. (Berkvnes 2001).
In general as table1 in results shows comparison made on prevalence of RVF in four
surveyed regions in Somaliland with their interval confidence respectively 95%, Sool has
19%, (0.18-0.25) Marodi jex15% (0.05-0.25) Sanaag 12% (0.11-0.15),Togdheer
0.11.%(0.10-0.14),
As result of prevalence Sool and Marodi jex has the highest prevalence of the disease and this
might be the movement of animals in Sool to Nugal valley which provide a favourable
condition to vectors for the growth of the vector prevails and provide a favourable condition,
exposing the area to reveal high case of positive RVF rising to the top of risk areas identified
in the study. Thus, the root cause of detecting the disease in such arid areas can be the change
of movement pattern of animals observed in the areas.
26

27. Admittedly, the landscape of these region with positive case can be allowing the disease to
get established as in shown in Map 3 in the result this study and these regions borders like
Ethiopia and surrounding districts have a large water catchment surface and at the same time
borders.
Sool located to Nugal which have a very large valley that often harbours the most favourable
condition for the survival and proliferation of Aedes spp (low elevation ground, high
temperature, superficial and underground rivers which supply sporadic natural pools
surrounded by dense vegetations) it found Grazing areas and watering points and the Sool
pastoral community moves towards the valley in search of water and pasture and this
movement is facilitated by the blood relation to the inhabitants in the valley while Marodi jex
pastoral communities moves towards Ethiopia also Marodi jex risk factor are plat and
watering point that is why become high at risk of disease also those districts have water
catchments and watering points that cause vector to be abundant.
Usually, the disease is basically dependent on the weather pattern in the study area as it is
vector. And in general Somaliland is termed to be laid in the Arid of east Africa giving that
RVF is very hard to get established in the area as endemic disease. After, 2000 embargo by
the Arab governments there launched a joint rift valley survey by Terra Nuova and Ministry
of livestock revealing that there was a recent out breaks or high viral circulation in Sanaag
and Sool which the recent outbreak idea was refuted as it did not happen before the study
however, the expectation of RVF outbreak was high.
As shows table 2 that sheep 49% are the least reared species when compared to goats 51%
while the herd is dominated by the female (60%) of herds and this is because, apart from
breeding, males (40%) are sold as source of cash for the household to cater other domestic
needs like sugar, drugs, food and clothes.
CHAPTER FOUR CONCLUSIONS AND RECOMMENDATION
5.1 Conclusion
This study was aimed at producing by mapping RVF of risk areas in Somaliland regions, so
that it can help to improve the management and control of RVF vector in those regions,
although the environment drivers that determine the life cycle of the vector with high risks
like Sool and Maroodi jex compared to Sanaag and Togdheer, the most importance to
27

28. identify and visualize areas of high rift valley fever in Somaliland is to put place areas which
are likely to become infected through sero- monitoring of those areas.
The sampling method using a GIS facilitated significantly the implementation of the RFV
investigation in Somaliland. in particular, high-risk areas of four regions in Somaliland. They
can be monitored and analysed newly available technologies of ArcGIS soft ware.
Similarly, a survey was carried out in Somaliland of screening sampling by using ArcGIS
software in 2001.
This mini thesis is important to create operational maps that could help the vector control and
priority areas of risk for disease control in future.
Hence, the maps were constructed to allow targeting with regions of high risk areas of RVF,
accordingly.
5.1 Recommendation
Based on finding of this study of mapping risk areas four of Somaliland regions, following
recommendations were given as follows
 Ministry of livestock and relevant veterinary NGO’s should develop the capacity to
identify ecological factors of mosquitoes to insure risk areas or create buffer zone.
 To make public awareness about controlling the vector and to avoid the spread of
disease in those regions.
 Those regions were at risk for the establishment of RVF and should provide
insecticide in human also Spraying could help the people to recover because the
disease can be transmitting through contact of tissue of the infected animals and
through mosquito bite from affected person to another person.
 Community to use proper dispose of trash or anything that hold water.
ANNEX ONE
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