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Autochtonous infection of dogs and slugs with Angiostrongylus vasorum in Hungary
Veterinary Parasitology 174 (2010) 351–354
Contents lists available at ScienceDirect
Veterinary Parasitology journal homepage: www.elsevier.com/locate/vetpar
Short communication
Autochtonous infection of dogs and slugs with Angiostrongylus vasorum in Hungary Gábor Majoros ∗ , Orsolya Fukár, Róbert Farkas Department of Parasitology and Zoology, Faculty of Veterinary Science, Szent István University, István u. 2, H-1078 Budapest, Hungary
a r t i c l e
i n f o
Article history: Received 3 February 2010 Received in revised form 9 September 2010 Accepted 14 September 2010 Keywords: Angiostrongylus vasorum French heartworm Canine angiostrongylosis Hungary
a b s t r a c t On the course of a helminthological survey of the dogs of Baranya County, Hungary Angiostrongylus vasorum infection was detected in two asymptomatic dogs. Identification of the parasite was based on morphology of the first-stage larvae (L1) isolated from droppings, and successful experimental infection with first stage larvae to laboratory reared Discus rotundatus and Lissachatina fulica snails, in order to exclude species of the family Filaroididae that have similar larvae to A. vasorum. While angiostrongylosis is widespread among foxes, this is the first report of A. vasorum infection in housedog in Hungary. In gardens, where infected dogs were being kept 91 specimens of 6 species of limacid and arionid slugs were collected of which 5 specimens of Arion lusitanicus were found to carry larvae of A. vasorum. Dogs usually do not ingest such large slugs willingly. Frogs are known to act as paratenic hosts in the life cycle of A. vasorum. Since one of the infected dogs harboured also infection with the intestinal trematode Alaria alata, of which frogs certainly play the role of the second intermediate host, therefore it is assumed that in this case the dog became infected with A. vasorum by eating frogs. © 2010 Elsevier B.V. All rights reserved.
1. Introduction Angiostrongylus vasorum (Baillet, 1866) Kamensky 1905, or French heartworm is a metastrongyloid parasitic nematode of domestic dog and wild canids. Several endemic foci or sporadic cases have been reported from North and South America, Africa, Australia and many European countries, especially in foxes (Bolt et al., 1994; Morgan et al., 2005; Tebb et al., 2007; Papazahariadou et al., 2007). In Hungary it has been reported in red foxes only (Sréter et al., 2003). Foxes are considered to be a reservoir for transmission of A. vasorum to domestic dogs (Poli et al., 1984; Bolt et al., 1992). There were no published data on its occurrence in dog in that country in spite of the fact that Kotlán
∗ Corresponding author at: István u. 2, H-1078 Budapest, Hungary. Tel.: +36 1 478 4275; fax: +36 1 478 4193. E-mail addresses: [email protected] (G. Majoros), [email protected] (R. Farkas). 0304-4017/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.vetpar.2010.09.012
(1960) mentioned the sporadic occurrence of this parasite in Hungary. The life history of A. vasorum was studied by Rosen et al. (1970), however it is still poorly understood (Morgan et al., 2005). The species has an indirect life cycle. Gastropods have been shown to act as intermediate hosts in experimental infections (Guilhon and Cens, 1973; Simpson and Neal, 1982; Bolt et al., 1992). Terrestrial snails and slugs are attracted to and eat canids’ faeces containing first stage larvae (Bolt et al., 1994). The definitive hosts may become infected by ingesting an intermediate host containing infective third instar larvae, either deliberately (Rosen et al., 1970) or unintentionally, while eating grass containing the infected gastropods or infective larvae shed in mollusc secretions or faeces (Guilhon and Cens, 1973; Morgan et al., 2005). Frogs are also implicated as paratenic hosts carrying the infective larvae and experimental work has demonstrated that they can also act as intermediate hosts (Bolt et al., 1993). European foxes occasionally eat frogs when they may be infected with A. vasorum
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G. Majoros et al. / Veterinary Parasitology 174 (2010) 351–354
Fig. 1. A characteristic L1 larva of Angiostrongylus vasorum isolated form faeces of dog. A prominent dorsal spine erects on the surface of a sharp tail end of larva with sinus wave curve and a small cup as a cephalic button emerge on the oral end.
(Robertson and Whelan, 1987). However, how the canids can be infected with this parasite species continues to be debated because the likelihood of the different pathways of infection is unknown. 2. Methods and results On the course of a curt survey of helminthoses of dogs to collect demonstration materials for veterinary students in 2003, two dogs were found to be infected with “lungworms” by presence of larvae in their faecal samples. These infected but asymptomatic dogs were kept in gardens of two neighbouring villages (Kislippó and Maty) SouthWestern Hungary, close to the flood area of the River Drava. A Baermann technique was applied to recover motile larvae from faeces. Thirty-six first instar nematode larvae with a length of between 300 and 350 m were detected in the faecal samples of two dogs. Some of these larvae were a little shorter than the first instar larvae of A. vasorum reported in the literature (Guilhon and Cens, 1973; Bolt et al., 1994) definitely through of their different maturity. However, their caudal ends showed a more or less wavy appearance with a dorsal spine that is characteristic for the larvae of this lung worm species and most of them had a cephalic button on the tip of head (Fig. 1). In consequence of morphological variability of the isolated larvae could not be distinguished from Filaroides/Oslerus larvae unequivocally because the species of later genera have similar larvae in some respects. Hence we had to do other examinations in the favour of confident diagnosis. In order to confirm the identity the parasites properly snails were infected with the isolated larvae under laboratory conditions. Greenhouse dweller European Discus rotundatus (O. F. Müller, 1774) and tropical Lissachatina fulica (Bowdich, 1822) specimens were used. The gastropods used in the experiment were bred from eggs in the lab. Seven young (4 mm in length) D. rotundatus and the
Fig. 2. A fully developed L3 larva of A. vasorum in the tissue of sole of naturally infected Arion lusitanicus pressed out of its second mould. It is a little larger as L3 of artificial infection. Its tail end is curled up with not an acute, wavy appearance but with a little blunt, fingerlike, conical tip.
same number of L. fulica (8 mm in length) were kept for 3 h in suspensions containing about 30 nematode larvae isolated from the faecal samples of the dogs using Petri dishes. Thereafter snails were transferred into transparent plastic boxes and kept at room temperature, feeding fresh lettuce. Ten days after exposure the snails were euthanatized then pieces of their bodies were compressed between two glass slides and examined for the presence of live nematode larvae. Molluscs were collected from the gardens where the infected dogs had been kept for years to study their natural rate of infection by larvae of A. vasorum and were examined the same as experimental snails. The larvae of A. vasorum were identified by their size and tail morphology (Ash, 1970; Rosen et al., 1970; Guilhon and Cens, 1973). Twelve specimens of live L2 and L3 larvae of A. vasorum were found in the connective tissues of experimentally infected D. rotundatus and L. fulica. The length of third stage larvae ranged between 500 and 560 m and their tail ends were digitiform, i.e. their shape was somewhat bended with a blunt tip as Ash (1970) mentioned it. The weakly sclerotised anterior part and the posterior muscular part of the oesophagus were not separated to each other so clearly as in case of similar Crenosoma larvae. The larger size and the characteristic form of the tail and oesophagus differentiated these larvae from the L3 of Angiostrongylus cantonensis and Crenosoma vulpis (or other Crenosoma species) which develop also in snails and may infect dogs (Ash, 1970; Baruˇs and Blaˇzek, 1971; Anderson, 2000). (The posterior end of the body ends in a sharp peak in both of the later species.) In the gardens of the 2 infected dogs, 91 specimens 6 slug species were collected (Table 1). The L3 larvae of A. vasorum were detected in only 5 juvenile specimens of Arion lusitanicus altogether. The pale brownish larvae were embedded in the loose perivisceral connective tissues but no larvae could be seen in the muscles of the foot or body wall. The shape of the lungworm larvae in these slugs looked just alike those in the experimentally infected snails except for the length of some larvae which reached 600 m (Fig. 2).
G. Majoros et al. / Veterinary Parasitology 174 (2010) 351–354
353
Table 1 Slugs were found in two gardens where the Angiostrongylus infected dogs were kept. Slug species
Arion lusitanicus (J. Mabille, 1868) Tandonia budapestensis (Hazay, 1880) Limax maximus (Linnaeus, 1758) Limax flavus (Linnaeus, 1758) Deroceras sturanyi (Simroth, 1894) Deroceras reticulatum (O. F. Müller, 1774)
Village Kislippó (collected/infected with larvae of Angiostrongylus vasorum)
Matty (collected/infected with larvae of A. vasorum)
15/1 1/0 1/0 0/0 4/0 3/0
29/4 0/0 0/0 1/0 30/0 4/0
One of the dogs proved to carry Alaria alata trematodes as well confirmed by the presence of their light yellow eggs. 3. Discussion Not only the morphology of the L1 but the experimental laboratory infection of two snail species with first instar nematode larvae found in the faecal samples of these dogs confirmed that A. vasorum caused the infection in both dogs. Applying the snails for confirmation of diagnosis of lungworm infection is suggested because of the morphology of larvae depends not only by species but also by their maturation process. In our cases the number of the isolated larvae was so small and their morphology was rather inconsistent as only their ability of development in snails could reveal the presence of species unequivocally. The larvae certainly were not equally “ripen” therefore none of all showed the typical morphology of A. vasorum L1 larvae. The ability of development in snail separated them from the Filaroides/Oslerus group, and after growing and moulting in tissue of snails the blunt end of the L3 larva made them distinguishable from the Crenosoma and other Angiostrongylus species that have tapered body ends in that period of development. According to the literature a variety of terrestrial and aquatic molluscs may act as intermediate hosts for this canid parasite (Rosen et al., 1970; Guilhon and Cens, 1973) including the tropical Achatina (=Lissachatina) fulica (Sauerländer and Eckert, 1974). The D. rotundatus is a small common dweller in leaf litter in European forest. Both snails were easily kept in laboratory and look useful experimental animals to rear Angiostrogylus larvae. Arion lusitanicus slug is known to consume faeces of different animal even dogs’ droppings (Bogon, 1990) and it was successfully infected by L1 of A. vasorum in lab previously (Guilhon and Cens, 1973). The natural infection of Arion lusitanicus with A. vasorum has proved first. More kind of slugs have been reported to carry larvae of A. vasorum and they can deliver infective larvae of this nematode species to dogs when these snails are consumed intentionally or accidentally (Guilhon and Cens, 1973). It is likely that the garden slugs were involved in the route of infection for these dogs. However, it cannot be excluded that these dogs became infected by ingesting infected paratenic hosts like frogs. It proved that frogs can act as a paratenic host of A. vasorum (Bolt et al., 1993), because snails may constitute a considerable part of the diet of wild frogs, e.g. the common frog (Rana temporaria) (Houston, 1973; Blackith and Speight,
1974). Danish studies suggested that frogs may act not only as paratenic hosts for A. vasorum, but also as intermediate hosts (Bolt et al., 1993). The detection of Alaria eggs in one of the two infected dogs clearly indicated the event of ingestion at least one frog by that animal: Life cycle of Alaria alata is indirect with a first intermediate host of an aquatic pulmonate snail (i.e. Planorbis planorbis or Anisus vortex) and a second one that is a tadpole of a frog. Alaria alata was frequently detected in red foxes and it was also found in dogs in Hungary (Széll et al., 2001). Domesticated dogs usually are not believed to consume frogs or snails (Bolt et al., 1994) but at least one of the dogs in all probability had eaten frogs as proved by eggs of Alaria alata in its faeces. Foxes certainly are the main reservoirs of A. vasorum (Bolt et al., 1994) and the most probable origin of infection of two dogs was also infected foxes. The continuously increasing number of red foxes and urbanization of this animal can lead on that parasites of foxes more often occur in dogs in the future (Morgan et al., 2005). Based on the anamnesis, these dogs acquired the infection locally, both of them were born where they lived and they never left their villages. Therefore their infection is considered autochthonous in Hungary similarly to other sporadic occurrences in Hungary that were not reported in detail previously (Kotlán, 1960). Acknowledgement We are grateful to Mónika Gyurkovszky for her technical assistance. References Anderson, R.C., 2000. Nematode Parasites of Vertebrates. Their Development and Transmission, 2nd ed. C.A.B. International, Wallingford, 578 pp. Ash, L.R., 1970. Diagnostic morphology of the third stage larvae of Angiostrongylus cantonensis, Angiostrongylus vasorum, Aelurostrongylus abstrusus and Anafilaroides rostratus (Nematoda: Metastrongyloidea). J. Parasitol. 56, 249–253. Baruˇs, V., Blaˇzek, K., 1971. The life cycle and the pathogenicity of the nematode Crenosoma striatum. Folia Parasitol. (Praha) 18, 215–226. Blackith, R.M., Speight, M.C.D., 1974. Food and feeding habitats of the frog Rana temporaria in bogland habitats in the west of Ireland. J. Zool. 172, 67–79. Bogon, K., 1990. Landschnecken: Biologie, Ökologie, Biotopschutz. Natur Verlag, Augsburg, Germany, 399 pp. Bolt, G., Monrad, J., Henriksen, P., Dietz, H.H., Koch, J., Bindseil, E., Jensen, A.L., 1992. The fox (Vulpes vulpes) as a reservoir for canine angiostrongylosis in Denmark. Field survey and experimental infections. Acta Vet. Scand. 33, 357–362. Bolt, G., Monrad, J., Frandsen, F., Henriksen, P., Dietz, H.H., 1993. The common frog (Rana temporaria) as a potential paratenic and intermediate host for Angiostrongylus vasorum. Parasitol. Res. 79, 428–430.
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Bolt, G., Monrad, J., Koch, J., Jensen, A.L., 1994. Canine angiostrongylosis: a review. Vet. Rec. 135, 447–452. Guilhon, J., Cens, B., 1973. Angiostrongylus vasorum (Baillet, 1866): Étude biologique et morphologique. Ann. Parasitol. Hum. Comp. 48, 567–596. Houston, W.W.K., 1973. The food of the common frog Rana temporaria on high moorland in northern England. J. Zool. 171, 153–165. Kotlán, S., 1960. Helminthologie. Die Helminthosen der Haus- und Nutztiere unter der Berücksichtigung der Helminthosen des Menschen. Akadémiai Kiadó, Budapest, 631 pp. Morgan, E.R., Shaw, S.E., Brennan, S.F., De Waal, T.D., Jones, B.R., Mulcahy, G., 2005. Angiostrongylus vasorum: a real heartbreaker. Trends Parasitol. 21, 49–51. Papazahariadou, M., Founta, A., Papadopoulos, E., Chliounakis, S., Antoniadou-Sotiriadou, K., Theodorides, Y., 2007. Gastrointestinal parasites of shepherd and hunting dogs in the Serres Prefecture, Northern Greece. Vet. Parasitol. 148, 170–173. Poli, A., Arispici, M., Marconcini, A., Mancianti, F., Monte, D., 1984. Angiostrongylus vasorum (Baillet, 1866) in red foxes (Vulpes vulpes L.) in Italy. J. Wildl. Dis. 20, 345–346.
Robertson, P.A., Whelan, J., 1987. The food of the Red fox (Vulpes vulpes) in Co. Kildare, Ireland. J. Zool. 213, 740–743. Rosen, L., Ash, L.R., Wallace, G.D., 1970. Life history of the canine lungworm Angiostrongylus vasorum (Baillet). Am. J. Vet. Res. 31, 131–143. Sauerländer, R., Eckert, J., 1974. Die Achatschnecke (Achatina fulica) als experimenteller Zwischenwirt für Angiostrongylus vasorum (Nematoda). Zeitschr. Parasitenk. 44, 59–72. Simpson, V.R., Neal, C., 1982. Angiostrongylus vasorum infection in snails and slugs. Vet. Rec. 111, 303–304. Sréter, T., Széll, Z., Marucci, G., Pozio, E., Varga, I., 2003. Extraintestinal nematode infections of red foxes (Vulpes vulpes) in Hungary. Vet. Parasitol. 115, 329–334. Széll, Z., Máthé, Á., Erdélyi, I., Deim, Z., Bende, Z., Varga, I., 2001. Spirocercosis and alariosis in dogs – short literature review and two rare case reports. Magy. Állatorv. Lapja 123, 421–428 (in Hungarian with English summary). Tebb, A.I., Johnson, V.S., Irwin, P.J., 2007. Angiostrongylus vasorum (French heartworm) in a dog imported into Australia. Aust. Vet J. 85, 23–28.
Contents lists available at ScienceDirect
Veterinary Parasitology journal homepage: www.elsevier.com/locate/vetpar
Short communication
Autochtonous infection of dogs and slugs with Angiostrongylus vasorum in Hungary Gábor Majoros ∗ , Orsolya Fukár, Róbert Farkas Department of Parasitology and Zoology, Faculty of Veterinary Science, Szent István University, István u. 2, H-1078 Budapest, Hungary
a r t i c l e
i n f o
Article history: Received 3 February 2010 Received in revised form 9 September 2010 Accepted 14 September 2010 Keywords: Angiostrongylus vasorum French heartworm Canine angiostrongylosis Hungary
a b s t r a c t On the course of a helminthological survey of the dogs of Baranya County, Hungary Angiostrongylus vasorum infection was detected in two asymptomatic dogs. Identification of the parasite was based on morphology of the first-stage larvae (L1) isolated from droppings, and successful experimental infection with first stage larvae to laboratory reared Discus rotundatus and Lissachatina fulica snails, in order to exclude species of the family Filaroididae that have similar larvae to A. vasorum. While angiostrongylosis is widespread among foxes, this is the first report of A. vasorum infection in housedog in Hungary. In gardens, where infected dogs were being kept 91 specimens of 6 species of limacid and arionid slugs were collected of which 5 specimens of Arion lusitanicus were found to carry larvae of A. vasorum. Dogs usually do not ingest such large slugs willingly. Frogs are known to act as paratenic hosts in the life cycle of A. vasorum. Since one of the infected dogs harboured also infection with the intestinal trematode Alaria alata, of which frogs certainly play the role of the second intermediate host, therefore it is assumed that in this case the dog became infected with A. vasorum by eating frogs. © 2010 Elsevier B.V. All rights reserved.
1. Introduction Angiostrongylus vasorum (Baillet, 1866) Kamensky 1905, or French heartworm is a metastrongyloid parasitic nematode of domestic dog and wild canids. Several endemic foci or sporadic cases have been reported from North and South America, Africa, Australia and many European countries, especially in foxes (Bolt et al., 1994; Morgan et al., 2005; Tebb et al., 2007; Papazahariadou et al., 2007). In Hungary it has been reported in red foxes only (Sréter et al., 2003). Foxes are considered to be a reservoir for transmission of A. vasorum to domestic dogs (Poli et al., 1984; Bolt et al., 1992). There were no published data on its occurrence in dog in that country in spite of the fact that Kotlán
∗ Corresponding author at: István u. 2, H-1078 Budapest, Hungary. Tel.: +36 1 478 4275; fax: +36 1 478 4193. E-mail addresses: [email protected] (G. Majoros), [email protected] (R. Farkas). 0304-4017/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.vetpar.2010.09.012
(1960) mentioned the sporadic occurrence of this parasite in Hungary. The life history of A. vasorum was studied by Rosen et al. (1970), however it is still poorly understood (Morgan et al., 2005). The species has an indirect life cycle. Gastropods have been shown to act as intermediate hosts in experimental infections (Guilhon and Cens, 1973; Simpson and Neal, 1982; Bolt et al., 1992). Terrestrial snails and slugs are attracted to and eat canids’ faeces containing first stage larvae (Bolt et al., 1994). The definitive hosts may become infected by ingesting an intermediate host containing infective third instar larvae, either deliberately (Rosen et al., 1970) or unintentionally, while eating grass containing the infected gastropods or infective larvae shed in mollusc secretions or faeces (Guilhon and Cens, 1973; Morgan et al., 2005). Frogs are also implicated as paratenic hosts carrying the infective larvae and experimental work has demonstrated that they can also act as intermediate hosts (Bolt et al., 1993). European foxes occasionally eat frogs when they may be infected with A. vasorum
352
G. Majoros et al. / Veterinary Parasitology 174 (2010) 351–354
Fig. 1. A characteristic L1 larva of Angiostrongylus vasorum isolated form faeces of dog. A prominent dorsal spine erects on the surface of a sharp tail end of larva with sinus wave curve and a small cup as a cephalic button emerge on the oral end.
(Robertson and Whelan, 1987). However, how the canids can be infected with this parasite species continues to be debated because the likelihood of the different pathways of infection is unknown. 2. Methods and results On the course of a curt survey of helminthoses of dogs to collect demonstration materials for veterinary students in 2003, two dogs were found to be infected with “lungworms” by presence of larvae in their faecal samples. These infected but asymptomatic dogs were kept in gardens of two neighbouring villages (Kislippó and Maty) SouthWestern Hungary, close to the flood area of the River Drava. A Baermann technique was applied to recover motile larvae from faeces. Thirty-six first instar nematode larvae with a length of between 300 and 350 m were detected in the faecal samples of two dogs. Some of these larvae were a little shorter than the first instar larvae of A. vasorum reported in the literature (Guilhon and Cens, 1973; Bolt et al., 1994) definitely through of their different maturity. However, their caudal ends showed a more or less wavy appearance with a dorsal spine that is characteristic for the larvae of this lung worm species and most of them had a cephalic button on the tip of head (Fig. 1). In consequence of morphological variability of the isolated larvae could not be distinguished from Filaroides/Oslerus larvae unequivocally because the species of later genera have similar larvae in some respects. Hence we had to do other examinations in the favour of confident diagnosis. In order to confirm the identity the parasites properly snails were infected with the isolated larvae under laboratory conditions. Greenhouse dweller European Discus rotundatus (O. F. Müller, 1774) and tropical Lissachatina fulica (Bowdich, 1822) specimens were used. The gastropods used in the experiment were bred from eggs in the lab. Seven young (4 mm in length) D. rotundatus and the
Fig. 2. A fully developed L3 larva of A. vasorum in the tissue of sole of naturally infected Arion lusitanicus pressed out of its second mould. It is a little larger as L3 of artificial infection. Its tail end is curled up with not an acute, wavy appearance but with a little blunt, fingerlike, conical tip.
same number of L. fulica (8 mm in length) were kept for 3 h in suspensions containing about 30 nematode larvae isolated from the faecal samples of the dogs using Petri dishes. Thereafter snails were transferred into transparent plastic boxes and kept at room temperature, feeding fresh lettuce. Ten days after exposure the snails were euthanatized then pieces of their bodies were compressed between two glass slides and examined for the presence of live nematode larvae. Molluscs were collected from the gardens where the infected dogs had been kept for years to study their natural rate of infection by larvae of A. vasorum and were examined the same as experimental snails. The larvae of A. vasorum were identified by their size and tail morphology (Ash, 1970; Rosen et al., 1970; Guilhon and Cens, 1973). Twelve specimens of live L2 and L3 larvae of A. vasorum were found in the connective tissues of experimentally infected D. rotundatus and L. fulica. The length of third stage larvae ranged between 500 and 560 m and their tail ends were digitiform, i.e. their shape was somewhat bended with a blunt tip as Ash (1970) mentioned it. The weakly sclerotised anterior part and the posterior muscular part of the oesophagus were not separated to each other so clearly as in case of similar Crenosoma larvae. The larger size and the characteristic form of the tail and oesophagus differentiated these larvae from the L3 of Angiostrongylus cantonensis and Crenosoma vulpis (or other Crenosoma species) which develop also in snails and may infect dogs (Ash, 1970; Baruˇs and Blaˇzek, 1971; Anderson, 2000). (The posterior end of the body ends in a sharp peak in both of the later species.) In the gardens of the 2 infected dogs, 91 specimens 6 slug species were collected (Table 1). The L3 larvae of A. vasorum were detected in only 5 juvenile specimens of Arion lusitanicus altogether. The pale brownish larvae were embedded in the loose perivisceral connective tissues but no larvae could be seen in the muscles of the foot or body wall. The shape of the lungworm larvae in these slugs looked just alike those in the experimentally infected snails except for the length of some larvae which reached 600 m (Fig. 2).
G. Majoros et al. / Veterinary Parasitology 174 (2010) 351–354
353
Table 1 Slugs were found in two gardens where the Angiostrongylus infected dogs were kept. Slug species
Arion lusitanicus (J. Mabille, 1868) Tandonia budapestensis (Hazay, 1880) Limax maximus (Linnaeus, 1758) Limax flavus (Linnaeus, 1758) Deroceras sturanyi (Simroth, 1894) Deroceras reticulatum (O. F. Müller, 1774)
Village Kislippó (collected/infected with larvae of Angiostrongylus vasorum)
Matty (collected/infected with larvae of A. vasorum)
15/1 1/0 1/0 0/0 4/0 3/0
29/4 0/0 0/0 1/0 30/0 4/0
One of the dogs proved to carry Alaria alata trematodes as well confirmed by the presence of their light yellow eggs. 3. Discussion Not only the morphology of the L1 but the experimental laboratory infection of two snail species with first instar nematode larvae found in the faecal samples of these dogs confirmed that A. vasorum caused the infection in both dogs. Applying the snails for confirmation of diagnosis of lungworm infection is suggested because of the morphology of larvae depends not only by species but also by their maturation process. In our cases the number of the isolated larvae was so small and their morphology was rather inconsistent as only their ability of development in snails could reveal the presence of species unequivocally. The larvae certainly were not equally “ripen” therefore none of all showed the typical morphology of A. vasorum L1 larvae. The ability of development in snail separated them from the Filaroides/Oslerus group, and after growing and moulting in tissue of snails the blunt end of the L3 larva made them distinguishable from the Crenosoma and other Angiostrongylus species that have tapered body ends in that period of development. According to the literature a variety of terrestrial and aquatic molluscs may act as intermediate hosts for this canid parasite (Rosen et al., 1970; Guilhon and Cens, 1973) including the tropical Achatina (=Lissachatina) fulica (Sauerländer and Eckert, 1974). The D. rotundatus is a small common dweller in leaf litter in European forest. Both snails were easily kept in laboratory and look useful experimental animals to rear Angiostrogylus larvae. Arion lusitanicus slug is known to consume faeces of different animal even dogs’ droppings (Bogon, 1990) and it was successfully infected by L1 of A. vasorum in lab previously (Guilhon and Cens, 1973). The natural infection of Arion lusitanicus with A. vasorum has proved first. More kind of slugs have been reported to carry larvae of A. vasorum and they can deliver infective larvae of this nematode species to dogs when these snails are consumed intentionally or accidentally (Guilhon and Cens, 1973). It is likely that the garden slugs were involved in the route of infection for these dogs. However, it cannot be excluded that these dogs became infected by ingesting infected paratenic hosts like frogs. It proved that frogs can act as a paratenic host of A. vasorum (Bolt et al., 1993), because snails may constitute a considerable part of the diet of wild frogs, e.g. the common frog (Rana temporaria) (Houston, 1973; Blackith and Speight,
1974). Danish studies suggested that frogs may act not only as paratenic hosts for A. vasorum, but also as intermediate hosts (Bolt et al., 1993). The detection of Alaria eggs in one of the two infected dogs clearly indicated the event of ingestion at least one frog by that animal: Life cycle of Alaria alata is indirect with a first intermediate host of an aquatic pulmonate snail (i.e. Planorbis planorbis or Anisus vortex) and a second one that is a tadpole of a frog. Alaria alata was frequently detected in red foxes and it was also found in dogs in Hungary (Széll et al., 2001). Domesticated dogs usually are not believed to consume frogs or snails (Bolt et al., 1994) but at least one of the dogs in all probability had eaten frogs as proved by eggs of Alaria alata in its faeces. Foxes certainly are the main reservoirs of A. vasorum (Bolt et al., 1994) and the most probable origin of infection of two dogs was also infected foxes. The continuously increasing number of red foxes and urbanization of this animal can lead on that parasites of foxes more often occur in dogs in the future (Morgan et al., 2005). Based on the anamnesis, these dogs acquired the infection locally, both of them were born where they lived and they never left their villages. Therefore their infection is considered autochthonous in Hungary similarly to other sporadic occurrences in Hungary that were not reported in detail previously (Kotlán, 1960). Acknowledgement We are grateful to Mónika Gyurkovszky for her technical assistance. References Anderson, R.C., 2000. Nematode Parasites of Vertebrates. Their Development and Transmission, 2nd ed. C.A.B. International, Wallingford, 578 pp. Ash, L.R., 1970. Diagnostic morphology of the third stage larvae of Angiostrongylus cantonensis, Angiostrongylus vasorum, Aelurostrongylus abstrusus and Anafilaroides rostratus (Nematoda: Metastrongyloidea). J. Parasitol. 56, 249–253. Baruˇs, V., Blaˇzek, K., 1971. The life cycle and the pathogenicity of the nematode Crenosoma striatum. Folia Parasitol. (Praha) 18, 215–226. Blackith, R.M., Speight, M.C.D., 1974. Food and feeding habitats of the frog Rana temporaria in bogland habitats in the west of Ireland. J. Zool. 172, 67–79. Bogon, K., 1990. Landschnecken: Biologie, Ökologie, Biotopschutz. Natur Verlag, Augsburg, Germany, 399 pp. Bolt, G., Monrad, J., Henriksen, P., Dietz, H.H., Koch, J., Bindseil, E., Jensen, A.L., 1992. The fox (Vulpes vulpes) as a reservoir for canine angiostrongylosis in Denmark. Field survey and experimental infections. Acta Vet. Scand. 33, 357–362. Bolt, G., Monrad, J., Frandsen, F., Henriksen, P., Dietz, H.H., 1993. The common frog (Rana temporaria) as a potential paratenic and intermediate host for Angiostrongylus vasorum. Parasitol. Res. 79, 428–430.
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