Prevalence and clinical aspects of human Trichostrongylus colubriformis infection in Lao PDR

Abstract

There have been few studies on human trichostrongyliasis in Southeast Asia, information on its clinical manifestations is also sparse. Trichostrongyliasis occurs predominantly in areas where poor hygiene is common especially where human/animal feces are used as a fertilizer, thereby contaminating vegetables and stream water. The intimate coexistence of domestic animals and humans explains the prevalence of Trichostrongylus infection in such areas. The goal of the current study was to determine the prevalence of trichostrongyliasis among villagers in Thakamrien village, Sonkon district, Savannakhet province, Laos, and to investigate potential relationships between clinical features, laboratory data, and severity of infection. Of 272 villagers examined, 160 (58.8%) were determined positive for helminthic infections by fecal examination, and 59 (36.9%) of these were infected with Trichostrongylus. Only 58 cases were in the inclusion criteria of the study and then underwent further assessment, including a questionnaire on personal behaviors, physical examination, and laboratory tests. Villagers in the trichostrongyliasis group were more likely than the control group to have consumed fresh vegetables, not washed their hands before meals or after using the toilet, and to have had close contact with herbivorous animals (goats and cows). Similarly, villagers in the trichostrongyliasis group were more likely than the control group to have a history of loose feces, rash, or abdominal pain; however, no obvious clinical symptoms were observed during physical examination of the trichostrongyliasis patients. The degree of infection was determined by both fecal egg counts and quantification of adult worms after deworming. Laboratory data were evaluated for any relationship with severity of infection. No significant differences were found in laboratory values between the trichostrongyliasis and control groups, with most values being within normal limits; however, both groups had high eosinophil counts. This study demonstrated that the useful clinical characteristics of trichostrongyliasis patients include history of loose feces, rashes, and abdominal pain, as well as in personal behaviors, such as the regular consumption of fresh vegetables, lack of hand washing, and close contact with cattle.

Introduction

Trichostrongylus colubriformis, a zoonotic nematode, normally lives in the digestive tracts, especially the small intestines, of domesticated and wild herbivorous animals, with the parasite's head embedded in the mucosa. Human infection occurs incidentally, by the ingestion of vegetation contaminated with infective 3rd-stage larvae. T. orientalis the most common species found in humans, while various other species are known to infect animals. Human infection is uncommon, but human trichostrongyliasis has occasionally been reported (Beaver et al., 1984, Boreham et al., 1995). A few trichostrongyliasis studies have been reported sporadically in Southeast Asia (Panasoponkul et al., 1985, Rim et al., 2003, Yong et al., 2007, Sato et al., 2010). Information on the disease in Southeast Asia, including its clinical presentation in humans, which is sometimes not mentioned in standard textbooks, is therefore sparse. The current study sought to determine the prevalence of Trichostrongylus infection among villagers in Savannakhet province, Laos, and investigate clinical symptoms, including laboratory data, linked to this disease.

Lao people favor consumption of raw or incompletely cooked foods with unique Lao dishes made of raw fish, beef, and pork. This habit is largely responsible for the spread of opisthorchiasis, sarcocystiasis, and taeniasis (Giboda et al., 1991). The lack of appropriate sanitary latrines is also a source of contamination and transmission of soil-transmitted helminthiases by Ascaris, Trichuris, and hookworm (Rim et al., 2003). The intimate coexistence of domestic animals and humans largely explains the prevalence of Trichostrongylus infection in the area (Giboda et al., 1991, Sato et al., 2010). The current study aimed to determine the prevalence of trichostrongyliasis among villagers in Thakamrien village, Sonkon district, Savannakhet province, Laos, and investigate clinical features and laboratory data linked to severity of infection.