Gastrointestinal nematodes infecting water buffalo: A comparison between Australia and Pakistan assessing species identification, prevalence and farming systems

Thom Williams

Research output: ThesisDoctoral Thesis

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Abstract

Gastrointestinal nematodes are the cause of significant negative health and production impacts in ruminant livestock systems worldwide. In developing countries such as Pakistan, the effects of gastrointestinal parasitism are often exacerbated by poor access to water and feed, a lack of infrastructure and limited information regarding management. Water buffalo are a ruminant livestock species most commonly farmed in developing countries. The recent interest for production in niche markets has led to population growth on farms in developed countries such as Australia. Globally, water buffalo are a significant dairy production species, producing 10% of the world’s milk. However, the impacts of gastrointestinal nematodes in water buffalo production systems are largely unknown.
Varying rates of gastrointestinal nematode infection in water buffalo from Pakistan have been previously reported (47.2–81.6%), however, no reports are available from Australia. Reports from Pakistan employed varying methodologies to identify infection which may account for the large variability in the results. Nonetheless, these rates of infection have been shown to cause significant negative production and health impacts in cattle farms elsewhere and similarities are expected in water buffalo systems. Management of gastrointestinal nematode infections has not been the focus of previous research. Age has been identified as influencing the likelihood of gastrointestinal nematode infection, but there is a large gap in the knowledge surrounding the effects of farming practices on the rate of infection.
The overall goal of this PhD research project was to advance the understanding of gastrointestinal nematode infections in two main farming systems; the smallholder cut-and-carry farms in Pakistan and the extensive grazing farms in Australia. The three primary objectives of this study were to 1) estimate the prevalence of gastrointestinal nematode infection in water buffalo from Australia and Pakistan; 2) describe current management used on farms and identify practices that affect the prevalence of gastrointestinal nematode infection in water buffalo across the two farming systems; and, 3) use morphological and molecular methods to describe the gastrointestinal nematodes species infecting water buffalo in Australia and Pakistan.
The investigation of gastrointestinal nematode prevalence in this study revealed unexpectedly low rates of infection in water buffalo in both Australia (8%) and Pakistan (30%). Strongyle-type nematode eggs were the most common morphotype observed during faecal egg counts accounting for 92% of infections in Australia and 98% of infections in Pakistan. Infections with other nematodes, Trichuris sp. (1.4% in Pakistan), Capillaria sp. (0.4% in Pakistan) and Toxocara vitulorum (0.4% in Pakistan and 8% in Australia) were also identified. Strongyle-type nematodes are considered the most agriculturally important species affecting ruminant livestock worldwide and may cause significant impacts to animal health if left unmanaged. Despite these worldwide trends, the low infection intensities observed in this study suggest strongyle-type nematodes have little impact on water buffalo farms in Australia and Pakistan. Although Trichuris sp., and Capillaria sp. are known to be mildly pathogenic, T. vitulorum is a parasitic species known to cause significant mortality and morbidity in water buffalo.
Recovered strongyle-type nematodes were identified using both L3 larvae morphology, and molecular characterisation of the ITS1 and ITS2 regions. Molecular identification revealed three nematode species that could not be described through current morphological keys or using molecular methods. These specimens most closely aligned with the genera Spiculopteragia, Oesophagostomum, and Trichostrongylus. Known species of agricultural importance, Cooperia sp., Trichostrongylus axei and Haemonchus sp., were also observed. Morphological identification of L3 larvae from water buffalo could be divided into morphometric groups that either 1) did not align with L3 larvae morphometrics previously described in identification keys; or, 2) had morphological characteristics that partially overlapped with previous descriptions of L3 larvae. These factors, coupled with the identification of undescribed species of strongyle-type nematodes, suggest current L3 larvae identification keys (designed for use in sheep and cattle) should not be employed to differentiate specimens recovered from water buffalo.
Analysis of on-farm management and its effects on gastrointestinal nematode prevalence revealed several management factors where farmers may intervene to reduce the likelihood of gastrointestinal nematode infection. In Pakistan, 19 predictors were identified as having a significant relationship with gastrointestinal nematode infection, eight of which were highlighted as the most critical factors through multivariate analysis. Body condition score (BCS), an indicator of animal health status, was considered the most influential predictor with BCS-1 water buffalo being 70% (CI = 0.14–0.58) more likely to be infected by gastrointestinal nematodes than BCS-3 water buffalo. In Australia, similar trends were observed, but no statistical validation was undertaken due to a small sample size and low levels of infection observed.
In both Australia and Pakistan, the prevalence of gastrointestinal nematode parasitism was associated with parasite transmission pathways and animal stressors (such as negative energy status or exposure of naïve livestock to high infective stage larvae loads). The practices identified in this study are also common in sheep and cattle operations, and when altered, have led to tangible reductions in gastrointestinal parasite prevalence.
To conclude, low overall prevalence of gastrointestinal nematode infections, coupled with low infection intensities suggest gastrointestinal nematodes do not pose a significant threat to animal health and production in water buffalo in the two farming systems investigated in this study. This contrasts with other ruminant farming systems, such as cattle, where gastrointestinal nematodes are estimated to cost the Australian industry 82.0M AUD per year. Despite the overall low frequency of infection and differing production systems employed in Australia and Pakistan, several farm management factors that affected the likelihood of gastrointestinal infection were identified across both countries. To reduce the incidence of infection, these factors could be used as critical points for farmers and their advisors to discuss/assess and lead to on-farm practice change. In addition, identification of strongyle-type species not described by current morphological identification keys highlights the need for an updated key that focuses on gastrointestinal nematodes recovered specifically from water buffalo. While the outcomes of this research can be applied to farming practices, diagnostics, and monitoring, several avenues of future research are warranted.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
  • Charles Sturt University
Supervisors/Advisors
  • Shamsi, Shokoofeh, Principal Supervisor
  • Jenkins, David, Principal Supervisor
Thesis sponsors
Place of PublicationAustralia
Publisher
Publication statusPublished - 2020

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