A combined parasitological molecular approach for noninvasive characterization of parasitic nematode communities in wild hosts

Abstract

Most hosts are concurrently or sequentially infected with multiple parasites; thus, fully understanding interactions between individual parasite species and their hosts depends on accurate characterization of the parasite community. For parasitic nematodes, noninvasive methods for obtaining quantitative, species-specific infection data in wildlife are often unreliable. Consequently, characterization of gastrointestinal nematode communities of wild hosts has largely relied on lethal sampling to isolate and enumerate adult worms directly from the tissues of dead hosts. The necessity of lethal sampling severely restricts the host species that can be studied, the adequacy of sample sizes to assess diversity, the geographic scope of collections and the research questions that can be addressed. Focusing on gastrointestinal nematodes of wild African buffalo, we evaluated whether accurate characterization of nematode communities could be made using a noninvasive technique that combined conventional parasitological approaches with molecular barcoding. To establish the reliability of this new method, we compared estimates of gastrointestinal nematode abundance, prevalence, richness and community composition derived from lethal sampling with estimates derived from our noninvasive approach. Our noninvasive technique accurately estimated total and species-specific worm abundances, as well as worm prevalence and community composition when compared to the lethal sampling method. Importantly, the rate of parasite species discovery was similar for both methods, and only a modest number of barcoded larvae (n = 10) were needed to capture key aspects of parasite community composition. Overall, this new noninvasive strategy offers numerous advantages over lethal sampling methods for studying nematode-host interactions in wildlife and can readily be applied to a range of study systems.

Uncertain links in host–parasite networks: lessons for parasite transmission in a multi-host system

“…As a result, it may not be possible for sampling efforts for nematodes to focus on the most under-sampled species identified in this study (red hartebeest, giraffe and steenbok), or even on those species for which no data were available (with the exception of missing domestic species such as goats). A non-invasive genetic method for identifying nematode communities from faecal samples has recently been demonstrated in African buffalo [80]. Genetic barcoding of parasites would provide an additional benefit in the form of evidence as to whether a parasite species identified in different host species is the same strain, as has been assessed for Haemonchus contortus in ungulates in Europe [81], and would remove the biases probably introduced by morphological identification of parasites, such as the presence of cryptic species.…”

Serum biochemistry panels in African buffalo: Defining reference intervals and assessing variability across season, age and sex

“…Between June 2008 and August 2012, an age-targeted cohort (median age 3.2 years, range 1–15 years) of female African buffalo were captured every 6 months for 4 years in KNP as part of a study on bovine TB [27–31]. Two hundred animals were originally captured from 3 locations spread across the Southern portion of KNP in 2008.…”

A comparison of two methods for quantifying parasitic nematode fecundity

“…At the end of a 4-year study on parasite interactions , buffalo were euthanized following the South African National Parks Standard Operating Procedure for Lethal Population Control. Aliquots representing 2.5% of the contents of the small intestine were collected following standard procedures (Wood et al 1995) and preserved in 5% phosphate buffered formalin as described in Budischak et al (2015). Adult nematode specimens were isolated by rinsing the samples through 250 and 44 μm sieves.…”

“…Specimens were stored in 70% ethanol and identified at the USDA Agricultural Research Service, US National Parasite Collection (USNPC), and Animal Parasitic Disease Laboratory. We chose to focus on C. fuelleborni since it was the most prevalent (94% of hosts) and abundant (96% of specimens) GI nematode in the study population (Budischak et al 2015). In utero and ex utero methods were applied to between 4 and 10 (mean ± se 8.2 ± 0.7) female C. fuelleborni specimens collected from each of ten buffalo.…”