Entamoeba infections in different populations of dogs in an endemic area of Lahore, Pakistan

Abstract

Entamoeba histolytica, a protozoan parasite that affects humans and other primates all over the world. It is a common waterborne pathogen in endemic areas that have fecal oral transmission cycle. The aim of the present study was to examine the prevalence of E. histolytica and other Entamoeba species cysts in three different dog populations. Fecal samples from 600 dogs were collected and processed to detect Entamoeba cysts using the triple fecal test (light microscopy) and fecal antigens of E. histolytica were detected using a fecal antigen ELISA (TechLab E. histolytica II). Because it is impossible to differentiate E. histolytica from Entamoeba dispar and E. moshkovskii, using light microscopy we referred to all cysts morphologically consistent with E. histolytica as E. histolytica/dispar/moskovskii to reflect this uncertainty. Samples from 197 household dogs without clinical signs, 122 samples from household dogs exhibiting clinical signs of diarrhea, dysentery and vomiting and 281 stray dogs with no specific clinical signs were examined. Entamoeba histolytica-like cysts were observed in 94 (15.6%, 95% CI=±3.88) by triple fecal test microscopy and E. histolytica antigens were demonstrated in 66 (11%, 95% CI=±4.41) by fecal antigen ELISA in 600 fecal samples. Significant differences (P≤0.05) in prevalence were found between the three populations. Twenty (10.1%, 95% CI=±7.86) and 11 (5.6%, 95% CI=±7.70) of 197 fecal samples from household dogs without clinical signs were positive by microscopy and by antigen ELISA, respectively. Twenty-nine (23.8%, 95% CI=±6.58) and 23 (18.8%, 95% CI=±7.81) of 122 the fecal samples from household dogs with clinical signs were positive by microscopy and by antigen ELISA, respectively. Forty-five (16.01%, 95% CI=±5.62) and 32 (11.3%, 95% CI=±6.38) of 281 fecal samples from stray dogs were positive by microscopy and by fecal antigen ELISA, respectively. Dogs from the youngest age group (6 months to 1 year) were more likely to be E. histolytica antigen positive than were dogs from the other two older age groups, with a significant difference (P≤0.05) between all age groups. Statistically, no significant (P≥0.05) difference of prevalence was seen in male and female dogs. The local dogs had the highest prevalence rate of E. histolytica antigens (36 of 246, 14.2%, 95% CI=±6.32) followed by imported breeds (11 of 115, 9.5%, 95% CI=±10.4) and crossbred (19 of 239, 8.3%, 95% CI=±7.47), indicating a significant (P≤0.05) trend of positivity between various breeds of dogs. These findings suggest that dogs may play an important role in the epidemiology of this pathogen.

Keywords: Cyst; Dog; Entamoeba histolytica; Household; Pathogen.