Trichuris vulpis and T. trichiura infections among schoolchildren of a rural community in northwestern Thailand: the possible role of dogs in disease transmission

Abstract

Background: Trichuriasis is an important soil-transmitted helminth infection caused by Trichuris trichiura. About one-tenth of the world population may be infected. Incidentally, T. vulpis or dog whipworm has been reported to infect humans based on the egg size. However, an overlapping egg dimension occurs between T. trichiura and T. vulpis leading to the potential for misdiagnosis. Objective: Develop a PCR method to differentiate T. trichiura and T. vulpis eggs in stool samples and to investigate the prevalence of both whipworms in humans and dogs in a rural community in Thailand. Materials and methods: We determined and compared the small subunit ribosomal RNA sequences of both species of whipworms for developing species-specific PCR diagnosis. After validation of the method, we conducted a cross-sectional survey at Ta Song Yang District in Tak Province, northwestern Thailand in 2008. Stool samples were randomly recruited from 80 schoolchildren (36 males, 44 females) and 79 dogs in this community. Results: Fifty-six individuals harbored Trichuris eggs in their stools. The PCR-based diagnosis revealed that 50 cases were infected with T. trichiura and six (10.7%) were co-infected with both T. trichiura and T. vulpis. Although the dimension of Trichuris eggs provided some diagnostic clues for species differentiation, a remarkable variation in the length of these whipworm eggs was observed among samples that could lead to misdiagnosis. Conclusion: Both T. trichiura and T. vulpis eggs were detected in stool samples of dogs that roamed around this community, highlighting the potential reservoir role of dogs in the transmission of both human and dog whipworms in this population.

Nested pcr based diagnosis of trichuriasis and appraisal of primer sensitivity and specificity for reliable detection in clinical samples

“…Although definite identification of T. trichiura in fecal specimens can be made on its characteristic egg, microscopic examination of fecal alone encounters misdiagnosis because of wide variations in egg dimension of T. trichiura and occurrence of overlapping dimension between Trichuris species (Yoshikawa et al 1989;Areekul et al 2010). In line with these findings from previous studies our study also revealed such variation in egg dimension of T. trichiura among school children of Southern Assam.…”

“…Contrary to our findings, a much higher prevalence of 66.8% was reported from a study carried out in West Malaysia using microscopic technique (Ngui et al 2011). A prevalence rate of 70.0% T. trichiura and 10.7% T. vulpis were observed in a rural community in northwestern Thailand using molecular technique (Areekul et al 2010). Studies conducted across the world revealed the significance of molecular diagnosis of SoilTransmitted Helminths over microscopy methods (Basuni et al 2011;Arndt et al 2013).…”

“…Ltd., New Delhi, India). The samples were then processed according to manufacturer's instructions except the final elution in 50µl of elution buffer FEB. / were used for T. trichiura and T. vulpis respectively, while a conserved primer HT18SR: 5 / -CTGTCCCAGTCACGAGAAC-3 / was used for both the species as described previously (Areekul et al 2010). Briefly, PCR amplifications were performed in a volume of 20µl with 100ng of sample DNA, 1µM of each primer, 1X PCR buffer, 2mM MgCl 2 , 1X BSA, 0.2mM dNTPs, and 1U of Taq DNA Polymerase (Thermo scientific, Wattham, USA) in the MJ Mini TM (Bio-Rad Laboratories, Hercules, CA) thermal cycler.…”

“…Trichuriasis has been increasingly recognized as an important public health concern among the soil-transmitted helminth (STH) infections worldwide with highest prevalence in Central Africa, Southern India, and Southeast Asia (Areekul et al 2010). Among the three zoonotic Trichuris species T. trichiura is considered as the predominant one with an estimate of 600 million infections worldwide, including 114 million preschoolage children and 233 million school-age children (Stephenson et al 2000;Ghai et al 2014).…”

Assessing the zoonotic potential ofAscaris suumandTrichuris suis: looking to the future from an analysis of the past

“…In contrast, the larger eggs of the dog whipworm, T. vulpis are more easily identified and several cases of humans cross-infected by T. vulpis have been described, even though most of these cases have not been properly evaluated (reviewed by Traversa, 2011). Recently Areekul et al (2010) used molecular methods and found that 11% of the Trichurispositive children in Thailand had T. vulpis eggs in their faeces, suggesting that this parasite should be considered a zoonosis in this area. Trichuris suis is a more obvious candidate than T. vulpis since it is phylogenetically more closely related to T. trichiura (e.g.…”