TREATMENT AND CONTROL METHODS IN PARASITOLOGY1 Part 2: Control Methods
INTRODUCTION The success of control measures against any disease is dependent on: - a knowledge of its aetiology (causative agent) - natural history epidemiology, including its mode of transmission, e.g. whether it is vector-borne, water-borne, or transmitted by orofaecal, aerosol or venereal methods. 2
CONTROL OF PARASITIC DISEASES Concepts of eradication, elimination, and control of parasitic diseases Education Environmental modification and cultural control Role of government, foundations and aid organisations 3
CONCEPTS OF ERADICATION, ELIMINATION, AND CONTROLOF PARASITIC DISEASES Eradication indicates that the parasite no longer exists anywhere in the world. Therefore is no need to maintain treatment regimes or control programmes. By contrast, if a parasite is merely controlled, then it continues to exist, though its incidence and prevalence, morbidity and mortality in particular areas will reduced as consequence of the ongoing control measures. 4
There are no example of successful parasite eradication campaigns. In many developed countries, may human parasites have been eradicated as a consequence of the rise in living standards, effective waste disposal, and improved hygiene. Improved meat hygiene inspection and concern over zoonotic diseases have lead to the virtual elimination of helmiths such as Enchinococcus granulosus and Taenia 5 saginata.
Control of any disease by the reduction of parasite load or vector population, thus reducing transmission, implies recognition that there is likely to be a continuing problem and hence commitment. The objective is to reduce the disease to a level at which it is acceptable to the community or the stockholder by reducing morbidity to levels commensurate with socioeconomic development or livestock productivity. 6
EDUCATION Parasitic infections tend to have their most severe impact upon those who are poorly educated But the risk of infection can often be reduced by simple changes in behaviour Education is a key feature of parasitic control programmes For example: if people understand that the large cysts that grow inside them result from eating and drinking substances that are contaminated with dog faeces, then theoritically it should be relatively easy to reduce the incidence of hydatid disease. 7 HOW?
BY MAKING THEM REASSESS THEIR RELATIONSHIP WITH DOG! 8
Educational materials leaflets, posters, radio and television programmes. Avoid scientific terminology, employing illustrations and photographs Some example of country that has good success: 1) China - So called „barefoot doctors‟ - Dispense simple treatment and verbal guidance to isolated communities. - Health messages often delivered via teachers - Health clinics provide opportunity to talk to women in the communities.* Women – often have a strong influence on the behaviour of all members in the family 9
2) Finland - During 1800s, hydatid disease was effectively controlled for many years through the provision of educational pamphlets. - Legislation and more effective treatments became available - By 1960s – the disease had been eliminated from the country. 10
Example of failure – Africa - Insecticide-treated bed-nets are effectively at preventing malaria, provided that they use it correctly - As a consequence, aid agencies in parts of Africa distribute free bed-nets and instruct them how to use it. - However the level of infant mortality still remains high. 11 - WHY?
The bed-nets are not always appropriate for the way people actually live. Such as burden to hang and disassemble the net everyday. The net traps heat difficult to sleep. Risks – fire, safety of the children They sleep outside of the house at night 12
ENVIRONMENTAL MODIFICATION AND CULTURAL CONTROL Until the development of effective drugs and pesticides, environmental modification and cultural control were the main means of combating parasites, pests and diseases. It was seldom understood why certain practices were effective but experience taught us to do or not to certain things at certain times of the year. In countries with seasonal climates, the risk of infection is often most pronounced at certain times of year and sometimes possible to predict when or whether a parasite will be particular problem and take appropriate action. 13
Relatively simple environmental modifications can reduce the risk of exposure to many parasites diseases. Example: 1)increasing the water flow rate in the irrigation channels and removing plant growth - unsuitable environment for the snails that acts as the intermediate hosts of schistosomes 2) concrete farm yards and animal pens - easy to keep clean of faeces 3) solid hut or house walls and ceiling - Do not provide hiding places for the hemipteran bug vectors of Trypanosoma cruzi 14
For ruminant parasitic species pasture and grazing management. Grazing management has an important role in parasite control. The aim of grazing management is to have vulnerable sheep exposed to fewer larvae on pasture. The result will be that fewer drenches will need to be used. At the same time grazing management provides nutrition to allow sheep to better deal with parasites. 15
Grazing paddocks alternately with sheep and cattle can exploit the fact that most of the common worms of sheep do not readily infect cattle, and vice-versa. The best method for alternate grazing of sheep and cattle is a 6-monthly interchange, with the sheep and cattle being swapped in January and July. 16
Cropping - The timing and duration of cropping is ideal for preparing paddocks that are virtually free of worm larvae. - This is because most larvae are removed with the crop, remaining larvae die because they are exposed to the sun and there is no contamination with worm eggs since the early autumn. 17
Preparation of Safe Pastures. - Safe pastures are those with low numbers of infective larvae.- Worm control can be greatly improved and drenching frequency reduced by preparing safe pastures for the most susceptible animals in the flock. 18
5% in hostPARASITE POPULATIONS –RARELY IN THE HOST 95% in pasture 19
BIOLOGICAL CONTROL Biological control is an ecological method designed by man for lower a pest or parasite population to keep these populations at a non harmful level. 20
STEP 1. Accurate identification of the pest species and confirmation of the pest as a target for biological control. STEP 2. Surveys for natural enemies (generally insects, mites, nematodes and diseases) are conducted in the area of origin of the pest STEP 3. Determine host-specificity of potential control organisms to assess impact on targets and nontargets and environmental safety. STEP 4. Following approval from federal and state regulatory officials, biological control agents are shipped to a domestic quarantine facility where they are examined to confirm species identity and to determine whether they are free of parasites and diseases. STEP 5. These agents are tested in field plots to determine that the agents do reduce densities of the target pest and do not have adverse effects on nontargets. Once this small scale testing is completed, appropriate natural enemies can be mass-reared to high numbers and released at field sites established by county biologists. STEP 6. Once released, each biological control agent is evaluated for establishment, spread, impact on the target species, and impact on nontarget species. Careful, long-term evaluation studies provide scientific data that are used to improve current and future programs. Additional releases may be made in an augmentative manner in systems where long-term stability of the natural 21 enemies is not feasible.
AGENTS FOR BIOLOGICAL CONTROL These organisms include1) Micro-arthropods - Biological control of insects may include predators (e.g. spider) parasites, parasitoids, (insect parasites of insects)2) Protozoa - Some protozoa such as Haemogregarina, Nosema, Babesia and Theileria are pathogenic for some parasites like "ticks"3) Predacious nematode - Steinernema (Neoaplectana) carpocapsae has shown some success against mosquitoes on an experimental level.4) Virus - Some potential candidate has been identified by not much known about them.5) Bacteria- Bacillus thuringiensis are among the most widely used antagonists in biological control of insects.- After ingestion, target insects are killed by a gut toxin which is released from crystal proteins in the bacterial spores 226) Fungi
NEMATOPHAGOUS-FUNGI Fungi that exhibit anti-nematode properties have been known for a long time. They are divided into three major groups based on their morphology and types of nematode-destroying apparatus1. Predacious Fungi2. Endo-parasitic Fungi3. Egg-parasitic Fungi 23
PREDACIOUS FUNGI Produce specialized nematode-trapping structures (adhesive knobs, networks, rings etc.) on the mycelium The trapping activity of the fungus was influenced by the motility of the infective larvae & there is no specificity for the parasitic species E.g Arthobotrys spp. (A. oligospora) - Cooperia oncophora - H. contortus or Ostertagia circumcincta Monacrosporium spp Duddingtonia flagrans 24
(A) Formation of the fungal trap (white arrow) after 6 h of the fungus/larva interaction (B) fungal trap in anastomosis (white arrow), forming the scattered adhesive three-dimensional network trap and septate conidium of the D. flagrans fungus (black arrow) (C) scattered adhesive three-dimensional network traps (white arrow) (D) fungal hyphae of the control without Ancylostoma spp. L3 (E) Ancylostoma spp. L3 in the control without fungus (F) Ancylostoma spp. L3 captured, after 8 h of interaction with the fungus, at the cephalic portion (white arrow) and at the middle of the body (black arrow) by traps in the anastomosis process (dashed white arrow). 26Maciel A. S., Araujo J. V., Campos A. K., Benjamin L. A., Freitas L. G., 2009. Scanning electron microscopyof Ancylostoma spp. dog infective larvae captured and destroyed by the nematophagous fungus Duddingtoniaflagrans. Micron 40(4): 463 – 470.
ENDO-PARASITIC FUNGI These invade nematodes either by penetration of cuticle from sticky spores adhering to the cuticle or following ingestion of spores which lodged in the gut. Inside the host, they develop an infectious thallus which absorbs the body contents. Endoparasitic fungi have no extensive hyphal development outside the body of the host except fertile hyphae such as evacuation tubes or conidiophores that release the spores. This type of fungi is obligate parasite of nematodes, with very limited capacity to develop outside the prey and density dependent E.g Drechmeria coniospora 27 Harposporium anguillulae
Shows conidia of fungus attached to Diagram of Drechmeria showing buccal (mouth) region of the salient features. nematode. Some spores have germinated and you can see faintly the sinuous hyphae of the parasite tracing through the body of the victim.Massive reproductive growth of 28conidiophores and conidia Conidia attached to tail region of nematode.of Drechmeria bursting through thecuticle of the host.
EGG-PARASITIC FUNGI These have the ability to attack the egg stage and may have a role in the control of animal parasites which have a long development and/or survival time in the egg stage in the environment outside host May be defined as fungal parasites of cyst and root-knot nematodes The fungus was shown to be able to degrade the egg shell enzymatically and infect the eggs E.g Paecilomyces lilacinus - Ascaridia galli and Parascaris equorum Verticillium chlamydosporium - Toxocara canis 29
Paecilomyces (A) Eggs of Ascaridia galli in Petri dishes of the control group (white arrows). (B) (B–D) Destroyed A. galli egg (white arrows) after interaction with the hyphae and chlamydospores of Pochonia chlamydosporia fungus (black arrows) 30F.R. Braga, J.V. Araújo, J.M. Araujo, L.N. Frassy, A.O. Tavela, F.E.F. Soares, R.O. Carvalho, L.M.Queiroz and J.H. Queiroz. 2012. Pochonia chlamydosporia fungal activity in a solid medium and itscrude extract against eggs of Ascaridia galli. Journal of Helminthology 86(03): 348-352.
INTEGRATED PARASITE MANAGEMENT (IPM) In livestock production Goal is not to create parasite-free animals. It is normal for sheep and goats to have parasites. Goal is to prevent clinical disease and production losses 31
Good Management Use of Clean or Safe Pastures Pasture Rest and Rotation Grazing Strategies Multi-species Grazing Alternative Forages Healthy Soil Nutritional Management Zero Grazing Genetics 33
GOOD MANAGEMENT Internal parasite control starts with good management and common sense. Sheep should not be fed on the ground. Feeders which cannot easily be contaminated with feces should be utilized for grain, hay, and minerals. Water should be clean and free from fecal matter. Pastures and pens should not be overstocked. When new sheep are acquired they should be isolated from the rest of the flock for 30 days and aggressively dewormed to prevent the introduction of drug-resistant worms. 34
USE OF CLEAN OR SAFE PASTURES Clean or safe pastures are pastures which are not contaminated with the worm larvae that affect sheep. Examples of clean pastures include: - pastures that have not been grazed by sheep or goats for the past 6 to 12 months; - pastures which have been grazed by horses or cattle; pasture fields in which a hay or silage crop has been removed; - pasture fields which have been rotated with field crops; and - pastures than have been recently established or renovated While burning a pasture will remove worm larvae, there are no pasture treatments that will effectively eliminate or reduce worm larvae. 35
PASTURE REST AND ROTATION It is a common misconception that rotational grazing helps to control internal parasites in sheep. Intensive rotational grazing may actually contribute to parasitic problems. This is because rotating large groups of sheep and lambs through small paddocks concentrates livestock and infective parasite larvae onto the same small area. 36
Researchers in the Netherlands found that it takes three months of rest for an infected pasture to return to a low level of infectivity. Researchers at Langston University (Oklahoma) determined that a 65-day rest period was sufficient (for goats). Rotational grazing is an effective management tool for managing parasites, but only if pasture rest periods are long enough (i.e. 60 days or more). On the other hand, better nutrition provided by rotational grazing may offset the effects of higher parasite loads on the pasture. 37
GRAZING STRATEGIES Approximately 80 percent of the worm larvae can be found in the first two inches of grass. Therefore, sheep grazing taller forages will have fewer parasite problems. Sheep should not be allowed to graze forages shorter than 2 inches in height. Sheep that browse also have fewer parasite problems. Another grazing strategy is to wait until the dew has lifted from the grass or grass has dried after a rain. Dry conditions force parasites to stay at the base of the plants where they are less likely to be consumed by the 38 livestock.
MULTI-SPECIES GRAZING Sheep (and goats) are generally not affected by the same internal parasites as cattle and horses. Consequently, pastures grazed by cattle and horses are safe(r) for sheep (and goats) and conversely. Sheep can be co-grazed with cattle and/or horses. A leader-follower system can be utilized or pastures can be alternated between sheep and cattle and/or horses. 39
There are numerous other benefits to multi-species grazing. Each species has different grazing behavior that complements one another. For example, sheep prefer to eat weeds and short, tender grasses and clover, while cattle prefer to eat taller grasses. Cattle may offer some protection from predators. 40
ALTERNATIVE FORAGES Some pasture plants have anthelmintic properties, such as those containing condensed tannins. Research has shown that sheep grazing tannin-rich forages have lower fecal egg counts than animals grazing traditional grass pastures. The tannins may also decrease the hatch rate of worm eggs and larval development in feces. 41
Forage species which contain high levels of condensed tannins include Sericea lespedeza, birdsfoot trefoil, and chicory. Sericea lespedeza is a warm, season legume. Birdsfoot trefoil is a long-lived perennial legume. Chicory is a low-growing, leafy perennial. Generally speaking, trees and shrubs contain higher levels of tannins than pasture grasses, and tropical legumes contain more condensed tannins than temperate legumes 42
HEALTHY SOIL Earthworms have been shown to ingest worm eggs and larvae, either killing them or carrying them below the soil surface. Certain types of fungi will trap and kill parasitic larvae. Dung beetles ingest and disperse manure, thus keeping eggs and larvae from developing. Anything that is done to maintain soil health and promote these types of organisms will aid in parasite control. Scientists are examining the possibility of feeding nematophagous fungi to livestock to kill larvae in manure piles. 43
NUTRITIONAL MANAGEMENT Supplemental feeding should not be overlooked as a means to control parasites. Sheep and lambs on a higher plane of nutrition mount a better immune response to internal parasites than animals whose nutritional status is compromised. Animals on low protein diets are more susceptible to infection because they produce less IgA (immunoglobulin). Higher levels of protein have been shown to improve the pregnant ewes immune response to parasites after lambing. Lambs receiving protein supplementation have reduced 44 fecal egg counts.
ZERO GRAZING Keeping sheep and/or lambs in confinement (i.e. "zero grazing") is a means of reducing parasitism and preventing reinfection. Under a zero grazing situation, sheep and/or lambs do not have access to any vegetation for grazing. They are housed in a bedded barn, dirt lot, or facility with slotted floors. Feed should be fed off the ground in feeders. Watering containers should be kept free from fecal matter. Slotted floors offer the best protection against internal parasites because sheep generally do not come into contact with their feces. 45
GENETICS Genetics is probably the best long term weapon against internal parasites in sheep. Some sheep breeds are more resistant and resilient to internal parasites. They include the Florida (or Gulf Coast) Native and the hair sheep breeds: St. Croix, Barbados Blackbelly (and its derivatives), and Katahdin. In Malaysia – Kalahari Red, Boer etc. Grazing resistant breeds of sheep with susceptible breeds, may act to “sweep” pastures and reduce contamination to susceptible animals. 46
ROLE OF GOVERNMENT, FOUNDATIONS AND AIDORGANIZATIONS Depends on co-ordinated national or even international responses which only can be achieved through the active cooperation of governments. Require stability within the country and a suitable infrastructure for distribution of funds, communication and travel for expert personnel. Can be organized through: - national government - local government - combination Only government have the power to pass and enforce legislation. 50
Legislation can be an effective tool: - can force local authorities to provide safe water and sanitation - make it an offence to import pets or domestic animals without a certificate- require farmers to dispose of dead animals appropriately. 51
Role of different organizational levels of health services in sleeping sicknesscontrol.(After World Health Organization, 1986.) 52