Study of the prevalence of capillaria hepatica in humans and rodents in an urban area of the city of Porto Velho, Rondônia, Brazil / Estudo da prevalência da Capillaria hepatica em humanos e roedores em área urbana da cidade de Porto Velho, Rondônia, Brasil

Introduction: Hepatic capillariosis, caused by Capillaria hepatica (Calodium hepaticum) (Bancroft, 1893), Travassos, 1915 (Nematoda, Trichinelloidea, Capillariidae), is a common zoonosis in rodents but is rare in humans. Seventy-two cases in humans have been reported worldwide since the first case was described by MACARTHUR in 192417,27. This study aimed to determine the prevalence of Capillaria hepatica in humans and rodents in an urban area of Porto Velho, the capital of Rondônia, in Brazil. Methods: After conducting a census of the area, 490 residents were randomly selected, and, after signing a term of consent, provided blood samples that were screened for anti-Capillaria hepatica antibodies. Simultaneously, rats were captured to assess the prevalence of this parasite in rodents by histopathological examination in liver sections. Results: A prevalence of 1.8% was found among residents who had specific antibodies at a dilution of 1:150, indicating exposure to parasite eggs; 0.8% of the subjects also had positive titers at a dilution of 1:400, indicating true infection. The prevalence in rats was 2%. Conclusions: The prevalence of infection with this parasite among humans and rats was low. While the prevalence encountered among humans was within the limits reported in the literature, the prevalence among rodents was much lower.

Introdução: Capilaríase hepática é causada pela Capillaria hepatica (syn. Calodium hepaticum) (Bancroft, 1893), Travassos, 1915 (Nematoda, Trichinelloidea, Capillariidae), sendo uma zoonose comum entre roedores, porém rara em humanos. Setenta e dois casos humanos foram relatados na literatura mundial desde o primeiro caso descrito por MACARTHUR em 192417,27. O objetivo desse estudo é determinar a prevalência da Capillaria hepatica em humanos e roedores de área urbana da cidade de Porto Velho, capital de Rondônia, Brasil. Método: Após realizar um censo da área, 490 moradores foram aleatoriamente selecionados e assinaram termo de consentimento, foram colhidas amostras de sangue para testar anticorpos anti-Capillaria hepatica. Simultaneamente, ratos foram capturados para determinação da prevalência deste parasita através do exame histopatológico em cortes de fígado. Resultados: Foi encontrada entre humanos prevalência de 1,8% de positividade para anticorpos específicos em diluição de 1:150, indicando exposição aos ovos do parasito; 0,8% desses também deram testes positivos quando seus soros sofreram diluição de 1:400, indicando infecção verdadeira. Nos ratos, a prevalência foi de 2%. Conclusão: A prevalência encontrada para o parasito entre homens e roedores foi baixa. Enquanto a prevalência encontrada entre humanos esteve dentro dos limites encontrados na literatura, a prevalência entre roedores foi bem menor.

Changes of cytokine mRNA expression and IgG responses in rats infected with Capillaria hepatica

The mRNA expression of several cytokines was evaluated in splenocytes and mesenteric lymph node (MLN) cells of rats infected with Capillaria hepatica by reverse-transcription (RT)-PCR until week 12 after infection. IgG1 and IgG2a, which are associated with Th1 and Th2 response, respectively, were also assessed by ELISA. The results indicated that the majority of cytokines, including the Th1 (IL-2 and IFN-gamma) and Th2 cytokines (IL-4, IL-5 and IL-10) were expressed at maximal levels during the early stage of infection (after week 1-2), and the ELISA data also evidenced a similar pattern of changes in IgG1 and IgG2a. Th1 and Th2 cytokines responded in a similar fashion in this rat model. The expression of cytokines in splenocytes was significantly higher than that in MLN cells, thereby indicating that cytokine production is controlled more by spleen than by MLN. In addition, the observation that IFN-gamma expression increased unexpectedly at the time of maximal egg production (6 weeks after infection) indicated that IFN-gamma is a cytokine reacting against egg production. However, increased IL-5 expression occurring in tandem with worm activity indicated that the activity of C. hepatica might be controlled by IL-5 expression.

Capillaria hepatica in rats: focal parasitic hepatic lesions and septal fibrosis run independent courses

Capillaria hepatica causes two main lesions in the liver of rats: multifocal chronic inflammation, directly related to the presence of disintegrating parasites and their eggs, and a process of systematized septal fibrosis. The comparative behavior of these two lesions was investigated in rats experimentally infected with 600 embryonated eggs, following either corticosteroid treatment or specific antigenic stimulation, in an attempt to understand the relationship between these two lesions, and the pathogenesis of septal fibrosis. The two treatments differently modified the morphological aspects of the focal parasitic-related lesions, but did not interfere with the presentation of diffuse septal fibrosis, although a mild decrease in the degree of fibrosis occurred in corticoid-treated animals. These findings indicate that although the two lesions are C. hepatica induced, they are under different pathogenetic control, the induction of septal fibrosis being triggered during early infection to follow an independent pathway.

Capillaria hepatica: a cause of septal fibrosis of the liver

Fine, long, fibrous septa were observed as a late change developing in the acinar zone III of the liver of rats experimentally infected with the helminth Capillaria hepatica. Hepatic septal fibrosis begun 30 days after inoculation of embryonated eggs into the stomach of rats and became clearly evident from the 40th day onwards. Experimental observation was undertaken for 170 days. Septal fibrosis increased progressively with time and was most marked when the parasitic nodules formed around larvae, disintegrating worms and eggs were involving. Septal fibrosis of the liver has not been previously recognized as a manifestation of hepatic capillariasis. The presence of sequestered parasite antigens, probably being slowly released within the liver, appears to be a major factor in the pathogenesis of hepatic septal fibrosis observed in rats with C. hepatica infection

Capillaria hepatica: alguns aspectos imunopatológicos da infecçäo espúria e da infeçäo verdadeira / Capillaria hepatica: some immunopathologic aspects of spurious and true infection

A fim de se observar uma possível proteçäo conferida pela infecçäo espúria contra uma infecçäo verdadeira por Capillaria hepatica, camundongos foram inoculados com ovos näo embrionados (infecçäo espúria) e, posteriormente, com ovos embrionados (infecçäo verdadeira). Anticorpos específicos da classe IgG, detectados por este imunoenzimático (ELISA), mostraram-se elevados a partir da segunda semana do experimento. O teste de hipersensibilidade cutânea tardia resultou negativo. O exame das lesöes do fígado, assim como a contagem de ovos, utilizados como parâmetros para comparaçäo entre os grupos de animais estudados, näo apresentaram variaçäo significativa indicando que a imunidade humoral induzida pela infecçäo espúria näo tem potencial protetor