Histopathological features and prevalence of Capillaria hepatica infection in Rattus spp. in Philippine Mount Makiling forest reserve and its adjacent areas

Abstract

Rats are recognized as reservoir hosts of several pathogens that pose a threat to human health. Although rats are reported to be hosts of a large number of pathogens, a survey of Capillaria hepatica carried by rats in various settings such as residential, agroforestry, and agricultural areas in the Philippines has not been conducted. A total of 90 rats composed of Rattus norvegicus, Rattus tanezumi, and Rattus exulans were collected through trapping in selected residential, agroforestry, and agricultural areas in Los Baños Laguna, Philippines. The overall prevalence of C. hepatica among rats was 21.11%. Among the rat species collected, R. norvegicus showed the highest prevalence (55.56%), followed by R. exulans (14.29%), then R. tanezumi (5.36%) (differences significant at p < 0.05). Moreover, residential areas had the highest prevalence of C. hepatica infection (50%), followed by agroforestry and agricultural areas at 6.7% each (significant at p < 0.05). However, the difference in C. hepatica infection between male (11.43%; 4/35) and female (27.27%; 15/55) rats was not significant (p > 0.05). Most of the infected rats were moderately infected (68.42%), while few were lightly and severely infected (15.78% each). Lastly, the presence of C. hepatica in liver is suggestive of presence of lymphocytes, amyloid, granuloma, and the occurrence of necrosis, hypertrophy, fibrosis, and cholestasis in the liver of the host. Capillariasis could be occurring in Philippine human populations, hence there is need for screening the population with appropriate means and to create awareness of this emerging disease.

Keywords: Capillaria hepatica; Histopathology; Liver; Philippines; Prevalence; Rats.

Fig. 1

Land cover of Los Baños Laguna, Philippines

Fig. 2

Relative intensity of C. hepatica infection as characterized by Childs et al. (1988). a Light, b Moderate, c Severe

Fig. 3

R. norvegicus liver infected with C. hepaticaa Yellowish lesions (yellow arrow) at the surface of liver suggesting the presence of C. hepatica, bC. hepatica with eggs (red arrow) inside (400×) obtained from an infected liver. Note the presence of striations and bipolar plugs as diagnostic feature of its egg (color figure online)

Fig. 4

Prevalence and relative intensity of C. hepatica infection between 35 male and 55 female rats (not significant, p > 0.05)

Fig. 5

Cross section of an infected liver showing a an adult worm and its stichocytes (black arrow) and bacillary bands (red arrow), b Councilman bodies (encircled), necrotic hepatocytes (green arrow), and hypertrophic hepatocytes (yellow arrow), c clustered C. hepatica eggs (asterisk) and amyloid deposition (orange arrow), d accumulation of bile (blue arrow) within the liver and presence of hypertrophic hepatocytes (yellow arrow) (400×) (color figure online)

Fig. 6

Fibrosis (F) and presence of granuloma (G) consisting of lymphocytes (asterisk) in a uninfected liver of Capillaria hepatica and bC. hepatica-infected liver showing carcass (black arrow) of C. hepatica eggs (400×)