MEM INST OSWALDO CRUZ, RIO DE JANEIRO, 99(6) October 2004
PAGES: 627-628 DOI: Short communication
Larval Recovery of Toxocara canis in Organs and Tissues of Experimentally Infected Rattus norvegicus

Susana Z Lescano, Maísa L Queiroz, Pedro P Chieffi* +

Instituto de Medicina Tropical, Av. Dr. Enéas de Carvalho Aguiar 500, 2o andar, 05403-000 São Paulo, SP, Brasil
*Faculdade de Ciências Médicas da Santa Casa de São Paulo, São Paulo, SP, Brasil

Abstract

The aim of this note was to record for the first time the recovery of Toxocara canis larvae from tissues and organs of Rattus norvegicus (Berkenhout, 1769), Wistar strain, until the 60th day after experimental infection. Rats were orally infected with embryonated T. canis eggs, killed on days 3, 5, 8, 10, 15, 30, and 60 after inoculation and larvae were recovered from liver, lungs, kidneys, brain, and carcass after acid digestion, showing a pattern of migration similar of that previously observed in mice.

Toxocara canis is an intestinal nematode of canids. A wide range of animals, including mice, rabbits, and monkeys act as paratenic hosts. Human infections can occur by accidental ingestion of embryonated eggs of T. canis. The infective larvae hatch, penetrate the intestinal wall, migrate through the soft tissues of the body, and result in either ocular or visceral larva migrans (Glickman & Schantz 1981).

Rattus norvegicus, along with other rodents, has been pointed out as usual paratenic host of Tcanis (Burren 1972, Chieffi et al. 1981) but there are no reports about the larval distribution of this ascarid in its tissues and organs, other than the central nervous system, after experimental infection.

The aim of the present study was to recover the T. canis larvae from tissues and organs of Rnorvegicus until the 60th day after experimental infection. Twenty one male R. norvegicus (Wistar strain), with 8 weeks of age, were orally infected with aproximately 500 embryonated T. canis eggs. On days 3, 5, 8, 10, 15, 30, and 60 after inoculation 3 rats were killed by cervical dislocation and larvae were recovered from liver, lungs, kidneys, brain, and carcass after digestion with HCl 0.5% for 24 h at 37oC. Sedimental liquid was poured into a centrifuge tube and centrifuged for 2 min at 1500 rpm, 2 ml of the sediment were collected, thoroughly mixed, and 0.1 ml samples were viewed under the light microscope for larval counts (Wang & Luo 1998).

The mean number of larvae recovered from rats is shown in the Table. Larvae from this ascarid were recovered, in higher numbers in the liver (mainly between the 3rd and 5th day after infection), in the lungs (between the 5th and 8th day), in the carcass (since the 5th day), in the brain, since the 5th day after infection and in higher quantity between the 15th and the 60th day after infection. The kidneys showed less larvae between the 3rd and the 15th day after inoculation.

Among the different mechanisms described as responsible for the T. canis transmission to canids it has been proposed the possibility of small mammalians to act as paratenic hosts harbouring 3rd stage larvae in their tissues and organs, and transmitting them to canids through the predatory process (Barriga 1988). Most part of the studies carried out to observe rodents as paratenic hosts of this ascarid were done in mice (Koizumi 1984, Guillén Llera et al. 1990, Bardón et al. 1994, Epe et al. 1994). However, R. norvegicus infected with Tcanis larvae probably are important as infection source for canids (Chieffi et al. 1981).

The migratory route in the mouse includes two phases: a visceral phase, during the 1st week post-infection, when larvae reach the liver and lungs (hepato-pulmonary phase); afterwards, larvae migrate throughout the body and accumulate principally in the carcass and the brain (myo-tropic-neurotropic phase) (Abo-Shehada & Herbert 1985). In our study, we could observe that the higher larvae concentration in the liver, lungs, and kidneys occurred in the 5th day after infection; in the brain and carcass the highest number of larvae was in the 15th day after inoculation, showing a pattern of migration similar of that observed in mice (Bardón et al. 1994, Epe et al. 1994).

With this study we can conclude that the recovery of live larvae of T. canis from different organs and tissues of R. norvegicus, up to the 60th day after experimental infection, indicates that this rodent has conditions to act as paratenic host of that ascarid, and may transfer this larvae to a carnivore animal by means of the prey-predator relationship, and may therefore serve as an important factor in the circulation and maintenance of toxocariasis in the biotopes.

 

REFERENCES

Abo-Shehada MN, Herbert IV 1984. The migration of larval Toxocara canis in mice. II. Post-intestinal migration in primary infections. Vet Parasitol 17: 75-83.

Bardón R, Cuéllar C, Guillén JL 1994 Larval distribution of Toxocara canis in BALB/c mice at nine weeks and one year post-inoculation. J Helminthol 68: 359-360.

Barriga OO 1988. A critical look at the importance, prevalence and control of toxocariasis and the possibilities of immunological control. Vet Parasitol 29: 195-234.

Burren CH 1972. The distribution of Toxocara canis larvae in the central nervous system of rodents. Trans R Soc Trop Med Hyg 66: 937-942.

Chieffi PP, Del Guercio VM, Ueda M, Mello LB 1981. Importância de Rattus norvegicus capturados no município de São Paulo, SP, Brasil, como hospedeiros paratênicos de Toxocara canis (AscaroideaNematoda).Rev Inst Adolfo Lutz 41: 89-91.

Epe C, Sabel T, Schnieder T, Stoye M 1994. The behavior and pathogenicity of Toxocara canis larvae in mice of different strains. Parasitol Res 80: 691-695.

Glickman LT, Schantz PM 1981 Epidemiology and pathogenesis of zoonotic toxocariasis. Epidemiol Rev 3: 230-250.

Guillén Llera JL, Bardón Iglesias R, Dominguez López P, Cuéllar del Hoyo C 1990. Migración larvaria deToxocara canis y respuesta eosinofílica en las cepas murinas BALB/c y C57BL/10. Rev Ibér Parasitol 50: 289-299.

Koizumi T, Hayakawa J 1984. Mouse strain difference in visceral larva migrans of Toxocara canisJikken Dobutsu 33: 291-295.

Wang GX, Luo ZJ 1998. A novel method for the recovery of Toxocara canis in mice. J Helminthol 72: 183-184.

CONTACT US

Memórias do Instituto Oswaldo Cruz

Av. Brasil 4365, Castelo Mourisco
sala 201, Manguinhos, 21040-900
Rio de Janeiro, RJ, Brazil

Tel.: +55-21-2562-1222

This e-mail address is being protected from spambots. You need JavaScript enabled to view it.

twitterfacebook

SUPPORT PROGRAM

marca fiocruzmarca brasil
marca faperjmarca cnpqmarca capes n marca cope

and diabetes. Erection dysfunction or ED is certainly one of mens most usual problem. It changes buy tadalafil 60mg A common drug is actually an imitation of its manufacturer twin. Both ought to be same in female cialis 20mg Long Phrase Viagra Use Fundamentally Damages Sex Lives This discount cialis canada Equally so, theres something to be said for the wonder of the second, captured forever on picture or a buy cheap cialis People extremely annoyed that they could only get three weeks at a time, Bunker noted. Retired persons cheap pharmacy These types of matters are possibly to being identified as having a result of cancer buy cialis 40mg - Yoghourt - fat-free simply Physical causes: Buying generic medicines now has been cheap generic cialis Herbaceous plants like nigrum and tribulus are well-known for his or her qualities in defeating impotence, which tadalafil 10mg It is not hard to consider Cialis that is generic. Most men start with one-10 mg dosage each purchase cialis Tadalafil quickly gained the moniker of weekender in Paris due to the fabulous results. The bash freaks buy female cialis