Giardia duodenalisisolates recovered from humans and dogs living in the same locality in a remote tea-growing community of northeast India were characterized at 3 different loci; the SSU-rDNA, elongation factor 1-alpha (ef1-α) and triose phosphate isomerase (tpi) gene. Phylogenetic analysis of the SSU-rDNA and ef1-α genes provided poor genetic resolution of the isolates within various assemblages, stressing the importance of using multiple loci when inferring genotypes toGiardia. Analysis of the tpi gene provided better genetic resolution and placed canineGiardiaisolates within the genetic groupings of human isolates (Assemblages A and B). Further evidence for zoonotic transmission was supported by epidemiological data showing a highly significant association between the prevalence ofGiardiain humans and presence of aGiardia-positive dog in the same household (odds ratio 3·01, 95% CI, 1·11, 8·39,P=0·0000).

Accurate quantitative assessment of infection with soil transmitted helminths and protozoa is key to the interpretation of epidemiologic studies of these parasites, as well as for monitoring large scale treatment efficacy and effectiveness studies. As morbidity and transmission of helminth infections are directly related to both the prevalence and intensity of infection, there is particular need for improved techniques for assessment of infection intensity for both purposes. The current study aimed to evaluate two multiplex PCR assays to determine prevalence and intensity of intestinal parasite infections, and compare them to standard microscopy. Faecal samples were collected from a total of 680 people, originating from rural communities in Timor-Leste (467 samples) and Cambodia (213 samples). DNA was extracted from stool samples and subject to two multiplex real-time PCR reactions the first targeting: Necator americanus, Ancylostoma spp., Ascaris spp., and Trichuris trichiura; and the second Entamoeba histolytica, Cryptosporidium spp., Giardia. duodenalis, and Strongyloides stercoralis. Samples were also subject to sodium nitrate flotation for identification and quantification of STH eggs, and zinc sulphate centrifugal flotation for detection of protozoan parasites. Higher parasite prevalence was detected by multiplex PCR (hookworms 2.9 times higher, Ascaris 1.2, Giardia 1.6, along with superior polyparasitism detection with this effect magnified as the number of parasites present increased (one: 40.2% vs. 38.1%, two: 30.9% vs. 12.9%, three: 7.6% vs. 0.4%, four: 0.4% vs. 0%). Although, all STH positive samples were low intensity infections by microscopy as defined by WHO guidelines the DNA-load detected by multiplex PCR suggested higher intensity infections. Multiplex PCR, in addition to superior sensitivity, enabled more accurate determination of infection intensity for Ascaris, hookworms and Giardia compared to microscopy, especially in samples exhibiting polyparasitism. The superior performance of multiplex PCR to detect polyparasitism and more accurately determine infection intensity suggests that it is a more appropriate technique for use in epidemiologic studies and for monitoring large-scale intervention trials. Gastrointestinal parasites including soil-transmitted helminths cause considerable morbidity worldwide, especially in resource-poor communities. Large-scale epidemiologic and treatment efficacy studies are regularly undertaken to determine the optimum ways to reduce or eliminate parasites from endemic communities, thereby reducing the burden of disease. Accurate and sensitive tests for detection of soil transmitted helminths and protozoa are of great importance to the success of such trials. Increasingly recognised is the importance of accurately determine the infection intensity, as morbidity and transmission pressure of helminth infections are directly related this and not just to prevalence. A vast majority of studies use standard microscopy methods which, although well accepted, may not be as accurate as more recently developed molecular techniques such as multiplex PCR. Therefore, there is need for further evaluation of multiplex PCR techniques and their ability to detect infections and provide infection intensity data. In the current study real-time PCR showed a higher sensitivity for the detection of intestinal helminths and protozoa especially in cases of mixed infections as well as more accurate determination of infection intensity compared to microscopy.