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Evaluation of the infectivity of Trichinella papuae and Trichinella zimbabwensis for equatorial freshwater fishes
Veterinary Parasitology 132 (2005) 113–114 www.elsevier.com/locate/vetpar
Evaluation of the infectivity of Trichinella papuae and Trichinella zimbabwensis for equatorial freshwater fishes E. Pozio *, G. La Rosa Department of Infectious Parasitic and Immunomediated Diseases, Istituto Superiore di Sanita`, viale Regina Elena 299, 00161 Rome, Italy
Abstract The discovery of Trichinella species infecting poikilotherm vertebrates has opened new possibilities in the epidemiology of this parasite group. The aim of the present work was to investigate the infectivity of the two non-encapsulated species of Trichinella infecting both mammals and reptiles, Trichinella papuae and Trichinella zimbabwensis, for equatorial freshwater carnivore fishes. To this end, two species of piranhas, four Serrasalmus nattereri and four Serrasalmus rhombeus, were each inoculated per os with the two species of Trichinella larvae. Six days post infection (p.i.), one fish of each species inoculated with one of the two species of Trichinella was sacrificed. The intestines and celomatic cavities were searched for worms using dissection microscopy, and the presence of muscle larvae was evaluated by artificial digestion. The other 4 inoculated fish were sacrificed 60 days p.i. and similarly searched for the presence of worms. No larva or adult worms were detected in any organ or tissue at 6 or 60 days p.i. The lack of infectivity of T. papuae and T. zimbabwensis for fish suggests that the entozoic habitat of this animal does not represent a suitable environment for these two Trichinella species. More importantly, these data indicate that freshwater fishes, one of the food resources for crocodiles, caimans and alligators, are unlikely to play a role in the epidemiology of the known species of the genus Trichinella. # 2005 Elsevier B.V. All rights reserved. Keywords: Trichinella; Freshwater fishes; Piranha; Serrasalmus nattereri; Serrasalmus rhombeus
1. Introduction The discovery of Trichinella species infecting poikilotherm vertebrates presents new and possibly undiscovered scenarios in the epidemiology of this parasite group (Pozio et al., 2002, 2004a). The biology of Trichinella papuae and Trichinella zimbabwensis * Corresponding author. Tel.: +39 06 4990 2304; fax: +39 06 4938 7065. E-mail address: [email protected] (E. Pozio).
allows them to complete their life cycle independently in a homotherm vertebrate (i.e., mammals) or in a poikilotherm vertebrate (i.e., reptiles), because these nematode species can develop at a temperature ranging from 25 to 40 8C (Pozio et al., 2004b). There are no reports of natural infections with Trichinella in lower vertebrate classes (i.e., amphibians and fishes) and all attempts to experimentally-infect these animals with encapsulated species of Trichinella or with the non-encapsulated species Trichinella pseudospiralis have thus far failed (Gaugusch, 1950;
0304-4017/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.vetpar.2005.05.038
114
E. Pozio, G.L. Rosa / Veterinary Parasitology 132 (2005) 113–114
Guevara Pozo and Contreras-Pena, 1966; Moretti et al., 1997; Tomasovicova, 1981). The aim of the present work was to investigate the infectivity of T. papuae and T. zimbabwensis for equatorial freshwater carnivore fishes.
2. Materials and methods As experimental model, we selected piranhas belonging to the species Serrasalmus nattereri and Serrasalmus rhombeus from Brazil because they live at water temperatures ranging from 25 to 32 8C where T. papuae and T. zimbabwensis are able to complete their life cycles in reptiles. Furthermore, the carnivorous nature of these fish makes them likely candidates to harbor a meat born parasite. Trichinella larvae were collected from muscles of experimentally-infected mice by artificial digestion according to standard methods (Pozio, 1987). All fish were inoculated per os with 1000 muscle larvae (ML) per animal. Four fish (two for each piranha species) received T. papuae and four additional fish (two for each piranha species) received T. zimbabwensis. As controls, Swiss-Webster mice were each inoculated with 500 ML from the same parasite preparations. One and three fishes for each Trichinella species were sacrificed 6 and 60 days post infection (p.i.), respectively, and the intestines and celomatic cavities were searched for adult worms using dissection microscopy. Artificial digestion of muscle tissue was used to search for muscle larvae.
3. Results and discussion No larva or adult worms were detected in any organ or tissue at 6 or 60 days p.i., whereas all control mice were infected 60 days p.i. In the past, experimental infections of fish with the encapsulated species T. spiralis and T. britovi and with the non-encapsulated species T. pseudospiralis showed that muscle larvae were unable to develop to the adult stage in the gut of fishes, but migrated from the gut to the muscles retaining their infectivity for some days p.i., until localized reactions within the host tissue destroyed the larvae (Moretti et al., 1997; Tomasovicova, 1981). In the present work, this phenomenon was not observed.
The lack of infectivity of T. papuae and T. zimbabwensis for freshwater fish maintained at 25– 32 8C, suggests that the entozoic habitat of these animals does not represent a suitable environment for these two Trichinella species. Though this does not rule out other fish species as potential sources of infection, we find this possibility highly unlikely. Consequently, it is doubtful that freshwater fish living in equatorial regions, one of the food resources for crocodiles, caimans and alligators, play a role in the epidemiology of the known species of the genus Trichinella.
Acknowledgement Work was funded by the Istituto Superiore di Sanita`, contract C3MO.
References Gaugusch, Z., 1950. Studies on the infection of poikilothermic animals with T. spiralis. Vet. Med. 5, 95–106. Guevara Pozo, D., Contreras-Pena, A.J., 1966. Trichinella spiralis Owen, 1835; Experiencias de infestacion en diversos vertebrados. Revista Iberica de Parasitologia 26, 239–288. Moretti, A., Piergili Fioretti, D., Pasquali, P., Mechelli, L., Rossodivita, M.E., Polidori, G.A., 1997. Experimental infection of fish with Trichinella britovi: biological evaluations. In: OrtegaPierres, G., Gamble, H.R., van Knapen, F., Wakelin, D. (Eds.), Trichinellosis. Centro de Investigacion y Estudios Avanzados IPN, Mexico City, pp. 135–142. Pozio, E., 1987. Isoenzymatic typing of 23 Trichinella isolates. Trop. Med. Parasitol. 38, 111–116. Pozio, E., Foggin, C.M., Marucci, G., La Rosa, G., Sacchi, L., Corona, S., Rossi, P., Mukaratirwa, S., 2002. Trichinella zimbabwensis n.sp. (Nematoda), a new non-encapsulated species from crocodiles (Crocodylus niloticus) in Zimbabwe also infecting mammals. Int. J. Parasitol. 32, 1787–1799. Pozio, E., Marucci, G., Casulli, A., Sacchi, L., Mukaratirwa, S., Foggin, C.M., La Rosa, G., 2004a. Trichinella papuae and Trichinella zimbabwensis induce infection in experimentally infected varans, caimans, pythons and turtles. Parasitology 128, 333–342. Pozio, E., Owen, I.L., Marucci, G., La Rosa, G., 2004b. Trichinella papuae in saltwater crocodiles (Crocodylus porosus) of Papua New Guinea: a potential source of human infection. Emerg. Infect. Dis. 10, 1507–1509. Tomasovicova, O., 1981. The role of fresh water fish in transfer and maintenance of Trichinellae under natural conditions. Biologia 36, 115–125.
Evaluation of the infectivity of Trichinella papuae and Trichinella zimbabwensis for equatorial freshwater fishes E. Pozio *, G. La Rosa Department of Infectious Parasitic and Immunomediated Diseases, Istituto Superiore di Sanita`, viale Regina Elena 299, 00161 Rome, Italy
Abstract The discovery of Trichinella species infecting poikilotherm vertebrates has opened new possibilities in the epidemiology of this parasite group. The aim of the present work was to investigate the infectivity of the two non-encapsulated species of Trichinella infecting both mammals and reptiles, Trichinella papuae and Trichinella zimbabwensis, for equatorial freshwater carnivore fishes. To this end, two species of piranhas, four Serrasalmus nattereri and four Serrasalmus rhombeus, were each inoculated per os with the two species of Trichinella larvae. Six days post infection (p.i.), one fish of each species inoculated with one of the two species of Trichinella was sacrificed. The intestines and celomatic cavities were searched for worms using dissection microscopy, and the presence of muscle larvae was evaluated by artificial digestion. The other 4 inoculated fish were sacrificed 60 days p.i. and similarly searched for the presence of worms. No larva or adult worms were detected in any organ or tissue at 6 or 60 days p.i. The lack of infectivity of T. papuae and T. zimbabwensis for fish suggests that the entozoic habitat of this animal does not represent a suitable environment for these two Trichinella species. More importantly, these data indicate that freshwater fishes, one of the food resources for crocodiles, caimans and alligators, are unlikely to play a role in the epidemiology of the known species of the genus Trichinella. # 2005 Elsevier B.V. All rights reserved. Keywords: Trichinella; Freshwater fishes; Piranha; Serrasalmus nattereri; Serrasalmus rhombeus
1. Introduction The discovery of Trichinella species infecting poikilotherm vertebrates presents new and possibly undiscovered scenarios in the epidemiology of this parasite group (Pozio et al., 2002, 2004a). The biology of Trichinella papuae and Trichinella zimbabwensis * Corresponding author. Tel.: +39 06 4990 2304; fax: +39 06 4938 7065. E-mail address: [email protected] (E. Pozio).
allows them to complete their life cycle independently in a homotherm vertebrate (i.e., mammals) or in a poikilotherm vertebrate (i.e., reptiles), because these nematode species can develop at a temperature ranging from 25 to 40 8C (Pozio et al., 2004b). There are no reports of natural infections with Trichinella in lower vertebrate classes (i.e., amphibians and fishes) and all attempts to experimentally-infect these animals with encapsulated species of Trichinella or with the non-encapsulated species Trichinella pseudospiralis have thus far failed (Gaugusch, 1950;
0304-4017/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.vetpar.2005.05.038
114
E. Pozio, G.L. Rosa / Veterinary Parasitology 132 (2005) 113–114
Guevara Pozo and Contreras-Pena, 1966; Moretti et al., 1997; Tomasovicova, 1981). The aim of the present work was to investigate the infectivity of T. papuae and T. zimbabwensis for equatorial freshwater carnivore fishes.
2. Materials and methods As experimental model, we selected piranhas belonging to the species Serrasalmus nattereri and Serrasalmus rhombeus from Brazil because they live at water temperatures ranging from 25 to 32 8C where T. papuae and T. zimbabwensis are able to complete their life cycles in reptiles. Furthermore, the carnivorous nature of these fish makes them likely candidates to harbor a meat born parasite. Trichinella larvae were collected from muscles of experimentally-infected mice by artificial digestion according to standard methods (Pozio, 1987). All fish were inoculated per os with 1000 muscle larvae (ML) per animal. Four fish (two for each piranha species) received T. papuae and four additional fish (two for each piranha species) received T. zimbabwensis. As controls, Swiss-Webster mice were each inoculated with 500 ML from the same parasite preparations. One and three fishes for each Trichinella species were sacrificed 6 and 60 days post infection (p.i.), respectively, and the intestines and celomatic cavities were searched for adult worms using dissection microscopy. Artificial digestion of muscle tissue was used to search for muscle larvae.
3. Results and discussion No larva or adult worms were detected in any organ or tissue at 6 or 60 days p.i., whereas all control mice were infected 60 days p.i. In the past, experimental infections of fish with the encapsulated species T. spiralis and T. britovi and with the non-encapsulated species T. pseudospiralis showed that muscle larvae were unable to develop to the adult stage in the gut of fishes, but migrated from the gut to the muscles retaining their infectivity for some days p.i., until localized reactions within the host tissue destroyed the larvae (Moretti et al., 1997; Tomasovicova, 1981). In the present work, this phenomenon was not observed.
The lack of infectivity of T. papuae and T. zimbabwensis for freshwater fish maintained at 25– 32 8C, suggests that the entozoic habitat of these animals does not represent a suitable environment for these two Trichinella species. Though this does not rule out other fish species as potential sources of infection, we find this possibility highly unlikely. Consequently, it is doubtful that freshwater fish living in equatorial regions, one of the food resources for crocodiles, caimans and alligators, play a role in the epidemiology of the known species of the genus Trichinella.
Acknowledgement Work was funded by the Istituto Superiore di Sanita`, contract C3MO.
References Gaugusch, Z., 1950. Studies on the infection of poikilothermic animals with T. spiralis. Vet. Med. 5, 95–106. Guevara Pozo, D., Contreras-Pena, A.J., 1966. Trichinella spiralis Owen, 1835; Experiencias de infestacion en diversos vertebrados. Revista Iberica de Parasitologia 26, 239–288. Moretti, A., Piergili Fioretti, D., Pasquali, P., Mechelli, L., Rossodivita, M.E., Polidori, G.A., 1997. Experimental infection of fish with Trichinella britovi: biological evaluations. In: OrtegaPierres, G., Gamble, H.R., van Knapen, F., Wakelin, D. (Eds.), Trichinellosis. Centro de Investigacion y Estudios Avanzados IPN, Mexico City, pp. 135–142. Pozio, E., 1987. Isoenzymatic typing of 23 Trichinella isolates. Trop. Med. Parasitol. 38, 111–116. Pozio, E., Foggin, C.M., Marucci, G., La Rosa, G., Sacchi, L., Corona, S., Rossi, P., Mukaratirwa, S., 2002. Trichinella zimbabwensis n.sp. (Nematoda), a new non-encapsulated species from crocodiles (Crocodylus niloticus) in Zimbabwe also infecting mammals. Int. J. Parasitol. 32, 1787–1799. Pozio, E., Marucci, G., Casulli, A., Sacchi, L., Mukaratirwa, S., Foggin, C.M., La Rosa, G., 2004a. Trichinella papuae and Trichinella zimbabwensis induce infection in experimentally infected varans, caimans, pythons and turtles. Parasitology 128, 333–342. Pozio, E., Owen, I.L., Marucci, G., La Rosa, G., 2004b. Trichinella papuae in saltwater crocodiles (Crocodylus porosus) of Papua New Guinea: a potential source of human infection. Emerg. Infect. Dis. 10, 1507–1509. Tomasovicova, O., 1981. The role of fresh water fish in transfer and maintenance of Trichinellae under natural conditions. Biologia 36, 115–125.