Dirofilaria infections in animals and
humans

Claudio Genchi, Med Vet, PhD, EVPC Dipl
Dept of Veterinary Science and Pub...
 Biology and epidemiology of Dirofilaria infections throughout
Europe and risk for public health
 Pathogenesis and clini...
Dirofilaria and D. immitis, the cruel worm of the dog: 400
years of history
Francesco Birago, a nobleman living in
Lomelli...
In 1850, Joseph Leidy, a physician and naturalist from
Philadelphia, described 3 worms found in the heart of a
dog as Fila...
In Europe, 5 filarial species has been reported in dogs and cats:
Dirofilaria immitis Leidy, 1856, Dirofilaria repens Rail...
Filarial parasite Vectors
Prepatent
period
Length of adult
worms
Location of
adult worms
Dirofilaria immitis
Mosquitoes
(C...
Dirofilaria diseases are vector-borne parasitic infections
mainly of dogs and cats (and wild carnivores) that in
Europe ar...
Distribution of Dirofilaria infection
The life cycle of both parasites consists of 5 larval stages developing
both within an intermediate mosquito host [from em...
Mosquito becomes infected taking blood from a microfilaraemic
host. Mf remain in the mosquito midgut for approximately 24 ...
Infective L3 are transmitted to the definitive host while the mosquito is
taking a blood meal: the tip of the labellum (fl...
When juvenile heartworms first reach the lungs and the heart,
the pressure of venous blood forces them into the small
pulm...
Dog: aduld worms are able to survive until 7 years
mf: until 12-18 months
usually infected both by male and female worms
C...
• Change in environmental ecology (global warming)
• Change in parasite ecology
• Decrease in natural resistance
• Economy...
The global average air temperature rose
0.74°± 0.18°C during the last 100 years
GLOBAL WARMING
Indeed, global climate chan...
Factors for the spreading and establishment of infections
in pets
Furthermore, great concern has arisen following the
intr...
Distibution of D. immitis in Italy: 1986-1988
Genchi et al., 1988. Atti IV Seminario SCIVAC
Since the first
epidemiologica...
Starating and ending period of Dirofilaria transmisson risk in 74 Italian1
provinces calculated for the decades 1980-1989,...
From south to north? From west to east?
Austria
Germany
Switzerland
Serbia
Albania
Bulgaria
Ucraine
Czech Republic
Hungary...
Country Year Prevalence (%)
No. of cases
Reference
Switzerland 1998 1.6%
8/479
Bucklar et al., Schweiz Arch
Tierheilk 1998...
Until recently, interest in Dirofilaria infections has been
focused primarily on D. immitis because of its
pathogenicity i...
Main factors allow the spread of Dirofilaria infection around
the world including socio/economic factors conditioning
the ...
Worming and introduction
of exotic mosquito
species in Italy as a
consequence of trade
exchanges
1990: Aedes albopictus
19...
Distribution D. immitis D. repens
Anophelinae
Anopheles claviger* N, S, Si, Sa - -
Anopheles maculipennis N, S, Si mol/fie...
Central Italy: mosquitoes CO2 trapped and PCR for
Dirofilaria worms [2002-2003]
Tested PCR positive
Mosquitoes Individuals...
The rate of Dirofilaria maturation to infective third-
stage larvae (L3) in the mosquito vector(s)
depends mainly on the e...
Temperature Dirofilaria immitis Dirofilaria repens
in Aedes spp.
28-30 °C
26 °C
22 °C
18 °C
8-9 days
10-14 days
17 days
29...
Temperature dictates the seasonal occurrence
of heartworm transmission in temperate
latitudes
 The total environment heat...
•A program was developed in order to calculate the
DDUs for 2556 European Meteorological Stations in
Europe
• Threshold va...
1971-2000: 854 examined meteorological stations
Meteorological stations reaching the 130DDUs based on
the average temperat...
Monthly average
predicted number of
HW generation
obtained by Linear
Kriging interpolation
May - November
ESCCAP Guideline 5, 2012
Control of vector-borne diseases
in dogs and cats
As for HW infection, D.
repens until recently w...
Currently subcutaneous D. repens infection is
diagnosed in Italy, France, Spain, Switzerland, Austria,
Germany, The Nether...
Host D. immitis D. repens A. reconditum Reference
Dog
[Vojvodina]
7.2% 49.2% 2.1% Tasić et al 2008
Humans >29 cases; most
...
5.1%
38.3%
18.5%
2%
D. immitis D. repens Location Reference
35%
23%
presence
3.5%
3.5% (1)
7%
0-31% (2)
presence
n.d.
n.d.
81%
presence (1)
17...
Geographic distribution of D. immitis in Romania [Ag Elisa]
Mircean et al, 2012 Vector-Borne Zoon Dis 12: 595-604
 Humans are susceptible hosts for dirofilarial worms
[accidental hosts]
 Usually the worm does not develop into adult st...
Human Dirofilaria repens infection in Europe: from
emergency to endemicity?
1900 - 1994: 267 cases 56/year
1995 - 1999: 26...
Country No.
cases
Ocular Pulmonary Other unusual and
seriousness localization
France
Greece
Hungary
Italy
Ukraine
Poland
R...
 Subcutaneous nodules
 Deep localizations intraperitoneal in lungs mimicking
tumors
 Ocular localization with impaired ...
Gherman 1967 (pers comm): hand dorsum
Olteanu 1997: many human cases, probably D. repens
Panaitescu et al, 2000: no data
M...
Typical features of D. repens are the external longitudinal ridges, the thick
cuticula, and the well-developed musculature...
… and recently the first case of Dirofilaria autochtonous
infection in has been diagnosed in Poland
Most studies have reported D. repens in animals
mainly from north-eastern European countries (i.e.:
north eastern Austria,...
 Intermediate hosts competence? D. repens microfilariae are more
easily destroyed by the bucco-pharyngeal armature of som...
 Most D. repens infections in dogs are asymptomatic while
HW infections usually cause severe clinical disease. It is
thus...
Dirofilaria immitis
Severe clinical signs
Mf in the blood by Knott test
Ag serology in dogs and Ab in
cats by Elisa
Very e...
Simpozion dirofilaria prezentare generala2013 1
Simpozion dirofilaria prezentare generala2013 1
Simpozion dirofilaria prezentare generala2013 1
Simpozion dirofilaria prezentare generala2013 1
Simpozion dirofilaria prezentare generala2013 1
Simpozion dirofilaria prezentare generala2013 1
Simpozion dirofilaria prezentare generala2013 1
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Simpozion dirofilaria prezentare generala2013 1

  1. 1. Dirofilaria infections in animals and humans  Claudio Genchi, Med Vet, PhD, EVPC Dipl Dept of Veterinary Science and Public Health, Università degli Studi of Milano Bucharest, June 14th, 2013
  2. 2.  Biology and epidemiology of Dirofilaria infections throughout Europe and risk for public health  Pathogenesis and clinical presentation: Dirofilaria immitis versus Dirofilaria repens  New insights in the prevention and treatment of canine and feline dirofilarial infections  Guidelines for the diagnosis of Dirofilaria infection in dogs and cats
  3. 3. Dirofilaria and D. immitis, the cruel worm of the dog: 400 years of history Francesco Birago, a nobleman living in Lomellina (Lombardy, Italy), in his Trattato Cinegetico ouero della Caccia (1626) made the first observation of heartworms during necropsy of an hunting dog and he wrote: The dog suffers of one more disease, which is not possible to be cured …. Two worms develop in the kidney. They are long as an half harm (Dioctophyma renale) wide as a finger and red as the fire … they move and migrate to the heart (Dirofilaria immitis)…
  4. 4. In 1850, Joseph Leidy, a physician and naturalist from Philadelphia, described 3 worms found in the heart of a dog as Filaria canis cordis In 1856, the same author redescribing the parasite, used for the first time the name of Filaria immitis The genus Dirofilaria, from the Latin, dirus (bad, cruel) and filum (thin, filiform), was erected in 1911 by Raillet and Henry in 1911, two parasitologists at the the School of Veterinary Medicine of Alfort, Paris.
  5. 5. In Europe, 5 filarial species has been reported in dogs and cats: Dirofilaria immitis Leidy, 1856, Dirofilaria repens Raillet and Henry, 1911, Dipetalonema dracunculoides Cobbold, 1870, Acanthocheilonema (syn. Dipetalonema) reconditum Grassi, 1890 (but a complete description of developmental stages in the fleas was done by Calandruccio, 1892), Cercopithifilaria (syn. Acanthocheilonema) grassii Noé, 1907.
  6. 6. Filarial parasite Vectors Prepatent period Length of adult worms Location of adult worms Dirofilaria immitis Mosquitoes (Culicidae) 120-180 days M: 12-18 cm F: 25-30 cm Pulmonary arteries/right heart Dirofilaria repens Mosquitoes (Culicidae) 189-259 days M: 5-7 cm F: 10-17 cm Subcutaneous tissue/muscular fasciae Acanthocheilonema (formerly Dipetalonema) reconditum Flies and ticks 427-476 days M: 9-17 mm F: 21-25 mm Subcutaneous tissue/muscular fasciae, peritoneal cavity, kidney Acanthocheilonema (formerly Dipetalonema) dracunculoides Fleas and ticks (R. sanguineus) 120 days M: 15-31 mm F: 33-55 mm Peritoneal cavity Cercopithifilaria spp. Ticks (R. sanguineus) ? M: unknown F: 23-24 mm Subcutaneous tissue/muscular fasciae www.ESCCAP.org Guideline 6 VBD
  7. 7. Dirofilaria diseases are vector-borne parasitic infections mainly of dogs and cats (and wild carnivores) that in Europe are caused by Dirofilaria immitis and D. repens and D. immitis only in the Americas. D. immitis, the cruel worm of dogs, is the causative agent of canine and feline heartworm disease. D. repens, is the causative agent of subcutaneous infections and its interest is mainly due to the high zoonotic potential.
  8. 8. Distribution of Dirofilaria infection
  9. 9. The life cycle of both parasites consists of 5 larval stages developing both within an intermediate mosquito host [from embryo - microfilaria - to infective L3), that also acts as vector, and in a definitive vertebrate host [from L3 to the adult worms]. Adult D. immitis worms occur in the pulmonary arteries and right heart chambers, causing a severe condition known as canine and feline heartworm disease, while D. repens is found mainly in subcutaneous tissues (subcutaneous dirofilariosis). Adult parasites released microfilariae in the blood stream where they are picked up by mosquitoes during their blood meal. The development from L3 to adult stages lasts 6-8 months.
  10. 10. Mosquito becomes infected taking blood from a microfilaraemic host. Mf remain in the mosquito midgut for approximately 24 h, then larvae become shorter and stouter (‘sausage’ stage). Larvae molt to the second stage 8 -10 days after infection and again to the third stage (L3) 2 - 3 days later. L3 perforate the distal ends of the Malpighian tubules and migrate to the head and mouthparts where they become infective (1100–1300 µm long). The time required for the development of microfilariae to the infective, third stage is temperature-dependent. At 27 °C and 80% relative humidity, development takes about 14 days. Biology
  11. 11. Infective L3 are transmitted to the definitive host while the mosquito is taking a blood meal: the tip of the labellum (fleshy part of the mouthparts) ruptures and the L3 are deposited on the skin in a drop of the mosquito’s haemolymph. Three days after infection, most of the larvae are found in the subcutaneous tissues near their entry site. By day 21, most of them have migrated to the abdomen of the dog, The molt from L3 to L4 begins as early as day 3 days and as late as day 9 - 12. L4 molt to the final stage [L5] at day 50 - 70; the first worms entering the pulmonary artery on day 70 - 85 are 2 - 4 cm in length. They become sexually mature (25-30 cm length) about day 120 post-infection. Dogs develop patent infections (circulating mf) as early as 6 months, but usually by 7 - 9 months post-infection. Biology
  12. 12. When juvenile heartworms first reach the lungs and the heart, the pressure of venous blood forces them into the small pulmonary arteries. As they increase in size, they migrate upstream into larger arteries until the worms become fully mature. The location of the adult worms depends on the size of the dog and the worm burden. A medium-sized dog with a low worm burden (i.e., 10) usually has worms mainly in the lobar arteries and main pulmonary artery. As the worm burden increases, worms are also located in the right ventricle. Dogs with more than 40 worms are likely to have caval syndrome, and most of worms migrate into the right ventricle, right atrium and the caudal vena cava, thus interfering with valvular function and/or blood flow. Biology
  13. 13. Dog: aduld worms are able to survive until 7 years mf: until 12-18 months usually infected both by male and female worms Cat: in most cases adult worms are able to survive 1½ year, but they can survive in asyptomatic cats until 4 years. Most cats are amicrofilaraemic, when present, mf can survive about 2 months frequently infected by male or female worms only, most infection abort (no adult worms in about 70% of cats) Biology
  14. 14. • Change in environmental ecology (global warming) • Change in parasite ecology • Decrease in natural resistance • Economy • Changed habit of human population Factors affecting the spreading of parasitic infections
  15. 15. The global average air temperature rose 0.74°± 0.18°C during the last 100 years GLOBAL WARMING Indeed, global climate change will affect disease vector behaviour, which in turn may alter the current patterns of vector-borne diseases transmitted by the bite of haematophagous arthropods (Rogers and Randolph, 2006). Arthropod vectors are cold- blooded animals, meaning that their internal temperature is greatly affected by the temperature of their environment (Purse et al, 2005).
  16. 16. Factors for the spreading and establishment of infections in pets Furthermore, great concern has arisen following the introduction of less restrictions in the movement of pets throughout European countries, which can increase the risk of spreading of arthropod-borne diseases, such as filarial infections In Practice 1999, 21: 482-491
  17. 17. Distibution of D. immitis in Italy: 1986-1988 Genchi et al., 1988. Atti IV Seminario SCIVAC Since the first epidemiological studies, north Italy, mainly the Po River Valley, has been shown the most endemic area for canine HW disease in Europe while D. repens was distributed mainly in central and south regions of the country
  18. 18. Starating and ending period of Dirofilaria transmisson risk in 74 Italian1 provinces calculated for the decades 1980-1989, 1990-1999 and 2000-2012.2 3 Decades 1980-1989 1990-1999 2000-2012 Transmission risk Number of weeks Number of days strating-ending 16 Apr - 8 Oct 25 175 strating-ending 16 Apr - 29 Oct 28 196 strating-ending 2 Apr – 6 Nov 31 217 4
  19. 19. From south to north? From west to east? Austria Germany Switzerland Serbia Albania Bulgaria Ucraine Czech Republic Hungary Hinaidy et al., J. Vet. Med., B 1987 34: 326-332 Reuther, Wschr Thierheilk 1888; 32: 429-430 Wenzel and Fallbericht, Kleintierpraxis 1898 34: 27-28 Leuterer and Gothe, Kleintierpraxis 1993 38: 633-646 Wohlsein and Brandes, Kleintierpraxis 1996 41: 367-374 Zahller et al., Tierärztl Prax 1997 25: 388-392. Arnold et al., Schweiz Arch Tierheilk 1994 136: 265-269 Deplazes et al., Schweiz Arch Tierheilk 1995 137:172-179 Bucklar et al., Schweiz Arch Tierheilk 1998 10 Tasić et al., Parasitol Res 2008 103: 1297-1302 Rapti and Rehbein, Parasitol Res 2010 107: 481-485 Georgieva et al., Bulgarian J Vet Med 1999 2: 121-124 Georgieva et al., Bulgarian J Vet Med 2001 4: 231-236 Mazurkevich et al., Vet Rec 2004 155: 638-639 Svobodova and Mišoňova, Vet Paasitol 2005 128: 137-140 Boros et al., Magyar Allatorvosok Lapja 1982 121 : 313-316 Zahler et al., Tierztlic. Praxis, 1997 25: 388-392 Szell et al., Magyar Allatorvosok Lapja 1999 121 : 100-104 Kleiter et al., Kleintierpraxis 2001 46: 283-288 Farkas, Helmithological Colloquium, 14th Nov, Vienna 2003
  20. 20. Country Year Prevalence (%) No. of cases Reference Switzerland 1998 1.6% 8/479 Bucklar et al., Schweiz Arch Tierheilk 1998 140:255-260 Germany June 1993 - May 1996 72 Zahller et al., Tierärztl Prax 1997 25: 388-392 The Netherlands 1992-1993 1982-1992 7 9 Meyer et al., Vet. Quartely 1994 16: 169-174 Tourism-associated canine Dirofilaria infection in northern Europe
  21. 21. Until recently, interest in Dirofilaria infections has been focused primarily on D. immitis because of its pathogenicity in companion animals. However, the increasing spread of D. repens towards eastern and northern Europe has renewed the interest for this species. Furthermore, human infections caused by D. repens are dramatically increasing in Europe. To note …
  22. 22. Main factors allow the spread of Dirofilaria infection around the world including socio/economic factors conditioning the abundance and movement animal reservoirs able to acts as donors of microfilariae to mosquitoes throughout a blood meal and mosquito species and abundance, however temperature plays a key role:  environmental temperature maintains/increases the abundance of competent mosquitoes  temperature is critical for the development of mf and for the duration of infection transmission season to new hosts
  23. 23. Worming and introduction of exotic mosquito species in Italy as a consequence of trade exchanges 1990: Aedes albopictus 1996: Aedes atroparvus 2011: Aedes koreicus
  24. 24. Distribution D. immitis D. repens Anophelinae Anopheles claviger* N, S, Si, Sa - - Anopheles maculipennis N, S, Si mol/field mol/field Culicinae Aedes albopictus N, S, Sa mol/field mol/filed Aedes cantans* N - - Aedes caspius* N, S, Si, Sa - - Aedes cinereus N mol/abd - Aedes geniculatus N, S, Si, Sa mol/abd - Aedes detritus N, S, Si, Sa mol/abd - Aedes punctor N, S mol/abd - Aedes vexans* N, S, Si, Sa - - Coquillettidia richiardii* N, S, Si, Sa mol/field - Culiseta annulata* N, S, Si, Sa - - Culex modestus N, S, Si, Sa mol/abd - Culex pipiens N, S, Si, Sa mol/field mol/field Culex torrentium N mol/abd - Culex territans* N, S - - Proven or suspected Culicidae vectors of D. immitis and D. repens in Italy (North: N; South: S; Sicily: Si; Sardinia: Sa); studies by dissection or PCR of field collected samples (mol/field). PCR positive abdomens (mol/abd) do not proving vector competence are also reported.
  25. 25. Central Italy: mosquitoes CO2 trapped and PCR for Dirofilaria worms [2002-2003] Tested PCR positive Mosquitoes Individuals Pools head-torax abdomen % Cx. pipiens Cx. hirritans Ae. albopictus Ae. caspius Ae. cinereus Cs. annulata 1,108 1 436 29 1 1 412 31 0 43 0 0 0 32 0 24 0 0 0 0.54 1.37 1 two D. repens, one D. immitis 2 one D. repens, two D. immitis 3 two D. repens, one D. immitis and D. repens 4 one D. repens and D. immitis Cancrini et al, 2007 Aedes albopictus: introduced in Italy in 1991 and proved Dirofilaria vector in 2003 Cx. pipiens: 1 two D. repens and one D. immitis, 2 one D. repens and two D. immitis Ae. albopictus: 3 two D. repens, one D. immitis; 4 one D. repens and one D. immitis
  26. 26. The rate of Dirofilaria maturation to infective third- stage larvae (L3) in the mosquito vector(s) depends mainly on the environmental temperature, and there is a threshold of about 14°C below which development will not proceed. Temperature dictates the development of Dirofilaria larvae in the intermediate hosts
  27. 27. Temperature Dirofilaria immitis Dirofilaria repens in Aedes spp. 28-30 °C 26 °C 22 °C 18 °C 8-9 days 10-14 days 17 days 29 days 8-10 days 10-11 days 16-20 days ~ 28 days in Ae. albopictus 26 °C 14-18 days 16-18 days Time requirements for Dirofilaria mf development to infective stage at different temperatures
  28. 28. Temperature dictates the seasonal occurrence of heartworm transmission in temperate latitudes  The total environment heat required for development may be expressed in terms of degrees days in excess of this threshold [Dirofilaria Development Units – DDUs]  The seasonal Dirofilaria transmission model assumes a requirement of 130 Heartworm DUs for larvae to reach infectivity and a maximum life expectancy of 30 days for a vector mosquito (Slocombe et al., 1989; Lok and Knight, 1998) Rationale
  29. 29. •A program was developed in order to calculate the DDUs for 2556 European Meteorological Stations in Europe • Threshold value of 130 cumulative DDUs was accepted only if it was reached in 30 consecutive days. •Data interpolated utilizing the Linear Kriging of GIS Model: Europe
  30. 30. 1971-2000: 854 examined meteorological stations Meteorological stations reaching the 130DDUs based on the average temperature of the 15 studied years May: 112 June: 356 July: 548 August: 550 September: 299 October: 65
  31. 31. Monthly average predicted number of HW generation obtained by Linear Kriging interpolation May - November
  32. 32. ESCCAP Guideline 5, 2012 Control of vector-borne diseases in dogs and cats As for HW infection, D. repens until recently was mainly present in northern Italy and southern of France. From 2000, the infection was more and more often diagnosed in northern-eastern countries.
  33. 33. Currently subcutaneous D. repens infection is diagnosed in Italy, France, Spain, Switzerland, Austria, Germany, The Netherlands, Poland, Czech Republic, Hungary, Croatia, Slovakia, Serbia, Romania, Greece, Russia Interestingly, in several countries the spreading of infection was firstly reported through human cases Pantchev et al: Diagnosis of imported canine filarial infections in Germany 2008- 2011. Pasitol Res 109 S61-S67 2011
  34. 34. Host D. immitis D. repens A. reconditum Reference Dog [Vojvodina] 7.2% 49.2% 2.1% Tasić et al 2008 Humans >29 cases; most ocular and periocular Kranijčić-Zec et al 1998 Džamić et al 2004 Džamić et al 2009 Tasić et al 2011 Serbia
  35. 35. 5.1% 38.3% 18.5% 2%
  36. 36. D. immitis D. repens Location Reference 35% 23% presence 3.5% 3.5% (1) 7% 0-31% (2) presence n.d. n.d. 81% presence (1) 17% n.d. whole country Bucharest area whole country Timiş County whole country south-western areas whole country Olteanu et al, 1996 Coman et al, 2007 Fernoagă et al, 2010 Ciocan et al, 2012 Hammer et al, 2012 Ilie et al., 2012 Micean et al, 2012 (1) Dogs imported from Romania to Germany (2) Depending on the region Prevalence of Dirofilaria infections in Romania
  37. 37. Geographic distribution of D. immitis in Romania [Ag Elisa] Mircean et al, 2012 Vector-Borne Zoon Dis 12: 595-604
  38. 38.  Humans are susceptible hosts for dirofilarial worms [accidental hosts]  Usually the worm does not develop into adult stage and humans are not microfilaremic, although at four cases of microfilaraemic zoonotic infections have been reported in Europe.  The severity of the infection depends on the localization of the parasite  Though the first case of D. immitis human infection has been found in Italy (histology and PCR), D. repens is the most frequent cause of zoonotic infection in Europe and Asia (more than 1500 cases vs 300-350 cases of HW human infections in USA and Japan)
  39. 39. Human Dirofilaria repens infection in Europe: from emergency to endemicity? 1900 - 1994: 267 cases 56/year 1995 - 1999: 264 cases 53/year 2000 - 2013: 1782 cases 137/year
  40. 40. Country No. cases Ocular Pulmonary Other unusual and seriousness localization France Greece Hungary Italy Ukraine Poland Russia (Siberia included) Turkey Other countries² 81 36 31 324 932 18 109¹ 22 229 22 7 19 62 18 44 12 120 2 1 23 2 intradural tumor like scrotum abdominal cavity spermatic cord, spermatic duct, scrotum intravitreal, 7 intra-oral cases in Sri Lanka, 16 scrotal, 2 spermatic cord, 1 testis, 1 epididymis, 1 associated with meningoencephalitis (surgery in Germany) Total 1782 305 27 ¹ Sergiev et al [65] reported of worms from 140 individuals identified as D. repens; such a figure has not been added to Russian cases because of incomplete description. ² Albania, Bulgaria, Croatia, Dubai, Former Yugoslavia, Georgia, Kazakhstan, Kenya, India, Iran, Israel, Japan, Malaysia, Poland, Romania, Serbia and Montenegro, Slovenia, Spain, Sri Lanka (more than 132 cases), Tunisia, Turkmenistan, Uzbekistan, USA Human D. repens infections published from 1900-2013
  41. 41.  Subcutaneous nodules  Deep localizations intraperitoneal in lungs mimicking tumors  Ocular localization with impaired vision and floater- like mobile shadow seem to be the most frequent symptoms, but infection is seldom accompanied by loss of vision or serious ocular complications; intravitreal ocular infection is quite rare but possible  The severity of the infection depends on the localization of the parasite Human infection
  42. 42. Gherman 1967 (pers comm): hand dorsum Olteanu 1997: many human cases, probably D. repens Panaitescu et al, 2000: no data Mănescu et al, 2009: a subcongiuntival nodule caused by D. repens Popescu et al, 2012: unusual and severe clinical manifestations that mimicked pathological conditions like cellulitis or deep venous thrombosis. The diagnosis was performed by histology and PCR. Romania
  43. 43. Typical features of D. repens are the external longitudinal ridges, the thick cuticula, and the well-developed musculature. Around the parasite a marked inflammatory reaction with numerous eosinophils, neutrophils, lymphocytes, plasma cells, and macrophages. Many IgE-positive plasma cells are present in the infiltration and near to the surface of the parasite
  44. 44. … and recently the first case of Dirofilaria autochtonous infection in has been diagnosed in Poland
  45. 45. Most studies have reported D. repens in animals mainly from north-eastern European countries (i.e.: north eastern Austria, Germany, The Netherlands, Hungary, Poland) and even when D. immitis is present, D. repens shows higher prevalences (i.e.: northern Serbia and Hungary). Human D. repens infections showed the same trend: the more recent and severe cases have been reported from north eastern countries such as Hungary, Slovak Republic, Poland, Russia and Romania. Why D. repens is spreading more rapidly than D. immitis?
  46. 46.  Intermediate hosts competence? D. repens microfilariae are more easily destroyed by the bucco-pharyngeal armature of some mosquito species (e.g.: Culex pipiens). Very few mf can develop to infective stage. In such a way, both the mosquito fitness and their ability to transmit the infection are not affected.  The spreading throughout Europe of Ae. albopictus. This species has shown to be infected by Dirofilaria larvae 2.5 times more than C. pipens, which is a proven intermediate hosts for dirofilarial worms.  D. repens has been found, when first established in the host, to be able to stimulate a specific immune response able to reduce the ability of D. immitis to develop into adult worms. Some hypothesis
  47. 47.  Most D. repens infections in dogs are asymptomatic while HW infections usually cause severe clinical disease. It is thus likely that dogs who travelled to endemic areas of southern Europe become infected and when they return to northern areas, having no apparent symptoms, act as donors of microfilariae to local mosquito populations. On the contrary, dogs with heartworm infection are usually referred to veterinary clinics and cured. If such an hypothesis is confirmed, considering that an increasing number of dogs travel for holidays or relocation and that pet travel is now facilitated by the new schemes in many European countries, subcutaneous dirofilarial infection could continue its spread. Some hypothesis
  48. 48. Dirofilaria immitis Severe clinical signs Mf in the blood by Knott test Ag serology in dogs and Ab in cats by Elisa Very effective preventative drugs Adulticide tharapy Apparently uncommon zoonotic infections in Europe Dirofilaria repens Mostly no clinical signs Mf in the blood by Knott test No serology Only moxidectin has been confirmed as an effective preventative No adulticide therapy Most common agent of human dirofilariosis in Europe

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