Occurrence of Fasciola hepatica (Linnaeus, 1758) in capybara (Hydrochoerus hydrochaeris) (Linnaeus, 1766) in Minas Gerais, Brazil / Ocorrência de Fasciola hepatica (Linnaeus, 1758) em capivara (Hydrochoerus hydrochaeris) (Linnaeus, 1766) em Minas Gerais, Brasil

Abstract Fasciola hepatica is a parasite that affects the hepatic ducts of several species of domestic and wild vertebrates, causing huge economic losses to livestock rearing worldwide. Reports on occurrences of F. hepatica in capybaras are an important epidemiological aspect of this disease, since these rodents can be a source of contamination for other animals and humans. In the present study, conducted in a rural area of the municipality of Confins, Minas Gerais, fresh feces from capybaras were collected from the ground near a lagoon at the edge of the Ribeirão da Mata river. These were examined using the technique of four metal sieves. F. hepatica eggs were recovered. This trematode species was confirmed by observing morphological characteristics and measuring the eggs recovered from the capybara feces, and through experimental infection of Lymnaea columella (Say, 1817) by miracidia from these eggs and subsequent infection of C57/BL06 mice with metacercariae originating from these infected mollusks. The data suggest the occurrence of natural cycle of F. hepatica in this region and provide a warning that expansion of the geographical distribution of this parasite by means of this rodent is possible. It is therefore important to adopting measures for epidemiological control of this helminthiasis.

Resumo Fasciola hepatica é um parasito que acomete os ductos hepáticos de diversas espécies de vertebrados domésticos e silvestres, causando grandes perdas econômicas na pecuária global. Relatos sobre a ocorrência de F. hepatica em capivaras constituem um importante aspecto epidemiológico dessa parasitose, visto que esses roedores podem ser fonte de contaminação para outros animais e humanos. No presente estudo realizado em área rural do município de Confins, Minas Gerais, foram coletadas no solo, próximo à lagoa marginal do rio Ribeirão da Mata, fezes frescas de capivaras. Essas foram examinadas pela técnica de quatro tamises metálicos. Foram recuperados ovos de F. hepatica. A confirmação da espécie desse trematódeo foi realizada por observação de características morfológica e mensuração dos ovos recuperados das capivaras, infecção experimental de moluscos Lymnaea columella (Say, 1817) por miracídios oriundos desses ovos e pela infecção de camundongos C57/BL06 com metacercárias oriundas desses moluscos infectados. Os dados obtidos sugerem a ocorrência do ciclo natural de F. hepatica na região, alertando que a expansão da distribuição geográfica deste parasito por esse roedor é possível. Portanto, é importante a adoção de medidas para o controle epidemiológico desta helmintíase.

A comparative study on mouse MHC class I sequences detected in Schistosoma japonicum recovered from BALB/c (H-2d) and C57BL/6 (H-2b) mice.

The mouse major histocompatibility complex (MHC) class I sequence was detected in all the 8-week-old Schistosoma japonicum recovered from BALB/c (H-2d) and C57BL/6 (H-2b) mice by in situ polymerase chain reaction (in situ PCR). The signals of the mouse class I MHC sequence were observed in the nuclei of the mesenchymal and reproductive cells of 8-week-old S. japonicum. Furthermore, the class I MHC sequence was detected in each DNA extracted from S. japonicum cercariae maintained in BALB/c and C57BL/6 mice by nested PCR. To prove both horizontal and vertical transmission of this sequence in schistosomes, we have used cercariae obtained from parasites maintained in BALB/c mice to infect C57BL/6 and BALB/c mice, and vice versa. The MHC sequences from adult worms were compared to the cercarial MHC and host MHC sequences. Nucleotide sequence comparisons between adult worm DNA, host (H-2d and H-2b mice) DNA and cercarial DNA used for the infection suggested that the sequence of mouse class I MHC was incorporated into schistosome adults and inherited throughout their life-cycle.

Characteristics of different isolates of Schistosoma japonicum from China in the final hosts.

The present paper deals with the susceptibility of common laboratory animals, such as mouse, rat, hamster, jird, rabbit and rhesus monkey, to infection with different isolates of Schistosoma japonicum in the mainland of China under laboratory conditions. With the exception of the rat, all the animals under study were permissive hosts for different isolates though their worm recovery rates varied. The mean body length of pair-worms of the Yunnan isolate was considerably smaller than that of the Anhui, Hubei, Guangxi and Sichuan isolates, and the percentage of male specimens with 7 testes in the Yunnan isolate was also significantly less than that in the other 4 isolates. Judging from the egg index (width/length x 100), the eggs of the Sichuan isolate were broad and short in shape, giving a high index; those of Guangxi and Hubei isolates were oblong, giving the lowest index; the other two isolates from Yunnan and Anhui, lay between these two extremes. The mean prepatent periods were longer in mice, hamsters and rhesus monkeys infected with Yunnan and Guangxi isolates, than those with Sichuan isolate. A dendrogram of the 5 isolates of S. japonicum was constructed on the basis of similarity coefficients by means of fuzzy cluster analysis on the biological characters mentioned above. Our results provide evidence of the existence of different strains of S. japonicum in the mainland of China as shown by comparative studies of their characteristics in the final hosts.