Wild Rodents as Experimental Intermediate Hosts of Lagochilascaris minor Leiper, 1909
Vol. 94(4): 441-449
Julieta Machado Paçô, Dulcinéa Maria Barbosa Campos+, Jayrson Araújo de Oliveira
Instituto de Patologia Tropical e Saúde Pública, Universidade Federal de Goiás, Setor Universitário, Caixa Postal 131, 74605-050 Goiânia, GO, Brasil
A total of 25 specimens of Cavia porcellus (guinea pig), 5 Dasyprocta agouti (agouti), and 22 Calomys callosus (vesper mice) were inoculated with infective eggs of Lagochilascaris minor. The inoculum was prepared with embryonated eggs and orally administered to each individual animal through an esophagus probe. In parallel, 100 specimens of Felis catus domesticus were individually fed with 55-70 nodules containing 3rd-stage larvae encysted in tissues of infected rodents. Animals were examined and necropsied at different time intervals. The migration and encystment of L3 larva was observed in viscera, skeletal muscle, adipose and subcutaneous tissues from all rodents. Adult worms localized at abscesses in the cervical region, rhino, and oropharynx were recovered from domestic cats inoculated with infected rodent tissues. Through this study we can conclude that: (1) wild rodents act as intermediate hosts, characterizing this ascarid heteroxenic cycle; (2) in natural conditions rodents could possibly act as either intermediate hosts or paratenic hosts of Lagochilascaris minor; (3) despite the occurrence of an auto-infecting cycle, in prime-infection of felines (definite hosts) the cycle is only completed when intermediate hosts are provided; and (4) in the wild, rodents could serve as a source of infection for humans as they are frequently used as food in regions with the highest incidence of human lagochilascariasis.
Key words: Lagochilascaris minor - heteroxenic cycle - intermediate host - paratenic host
The genus Lagochilascaris was described after specimens obtained from subcutaneous lesions of two patients in Trinidad. This nematode has both peculiar morphology and habits. To date, five species have been recognized in this genus: L. minor Leiper, 1909; L. major Leiper, 1910; L. turgida (Stossich, 1902) Travassos, 1924; L. sprenti (Bowman et al. 1983) and. L. buckleyi Sprent, 1971.
Human lagochilascariasis is caused by L. minor and it is considered an emerging helmintiasis limited to the American continent. The parasitosis is not yet a public health problem. Nevertheless, it is prevalent in individuals of the lowest social-
economic class, notably from rural areas. Lagochilascaris pathogenicity varies from mild manifestations to more severe forms, involving the central nervous system, which in some cases may lead to death (Rosemberg et al. 1986, Orihuela et al. 1987).The parasite is frequently found in tumoral lesions at the cervical region and neighboring tissues. Human L. minor lesions have been reported in the mastoid, tonsils, eyeball, neck, nasal sinuses, middle ear, central nervous system, lungs, rhino pharynx, dental alveolus, cervical region, and sacral region (Fraiha et al. 1989, Bento et al. 1993). Lagochilascaris lesions contain different stages of the parasite which indicates potential auto-infection and favours the development of chronic disease (Campos et al. 1983, Moraes et al. 1985).
Reported human infections have neotropical distribution in countries such as Mexico, Costa Rica, Trinidad, Tobago, Colombia, Venezuela, Suriname, Bolivia and Brazil (Olle-Goig et al. 1996, Vargas-Ocampo & Alvarado-Aleman 1997, Paçô & Campos 1998). Moreover, Brazilian Amazon currently represents an important focus of the helmintiasis (Fraiha et al. 1989). It is suggested that the Brazilian Amazon, especially the region between Tocantins and Araguaia rivers, presents the best ecological resources for Lagochilascaris development.
L. minor infection through ingestion of either uncooked or lightly cooked meat containing encysted larvae was hypothesised by Smith et al. (1983) and later confirmed by Campos et al. (1992). As yet, natural hosts for L. minor are unknown. However, it seems reasonable to believe that such a host exists because most patients infected with L. minor come from woody areas. In general, infected individuals in small newly deforested areas work upon the land for subsistence and feed almost exclusively upon hunted meat (Campos et al. 1991, Paçô 1994).
Taking into consideration the feeding habits of patients with lagochilascariasis and experimental data that demonstrate the heteroxenic cycle for the helminth, we decided to investigate the potential susceptibility of some wild rodent species, frequently used as food source in regions of high prevalence of L. minor infection. In our study wild rodents were inoculated with infecting eggs of L. minor while domestic cats were fed carcasses of infected rodents.
ACKNOWLEDGEMENTS
To the local Zoo, the Jardim Zoológico de Goiânia, for donating specimens of Dasyprocta agouti.
Fig. 1 | Fig. 2 | Fig. 3 | Fig. 4 | Fig. 5 | Fig. 6 | Fig. 7
Table I | Table II
+Corresponding author. Fax: +55-62-202.3066. E-mail: dmcampos@ufg.br
Received 10 July 1998
Accepted 18 March 1999
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