Abstract
Smallholder large ruminant production in Lao People’s Democratic Republic (Laos) is characterised by low reproductive efficiency. To determine if common abortifacient bovid infectious diseases are involved, a serological investigation was conducted. Sera was collected from stored and fresh cattle (n = 390) and buffalo (n = 130) samples from 2016–18 from, and then examined for associations in a retrospective risk factor study of 71 herds. The sera were assayed for antibodies to Neospora caninum, bovine viral diarrhoea virus (BVDV), Leptospira interrogans serovar Hardjo and Brucella abortus using commercially available enzyme-linked immunosorbent assay kits. These pathogens were detected in buffalo samples at 78.5% (95% CI 71.4–85.6), 0%, 2.3% (95% CI 0–4.9) and 0%, respectively, and in cattle at 4.4% (95% CI 2.4–6.4), 7.7% (95% CI 3.1–12.3), 12.8% (95% CI 9.5–16.1) and 0.26% (95% CI 0–0.8), respectively. Exposure of buffalo to N. caninum was positively associated with buffalo age, with a predicted seropositivity at birth of 52.8%, increasing to 97.2% by 12 years of age (p = 0.037). Exposure of cattle to L. interrogans serovar Hardjo was more prevalent in females compared to males, was associated with higher titres of BVDV, and was more prevalent in the wet season compared to the dry season. Exposure of cattle to BVDV was more prevalent in males compared to females, the wet and dry seasons were comparable, and was associated with rising antibody titres against N. caninum and L. interrogans serovar Hardjo. The risk factor survey identified that the probability of herds being N. caninum positive increased with farmer age, if farmers believed there were rodents on farm, and if farmers weren’t aware that canids or rodents could contaminate bovid feed on their farm. The probability of a herd being positive to L. interrogans serovar Hardjo increased on farms where multiple cows shared the same bull, where farmers had lower husbandry knowledge, and on farms that used water troughs. The probability of a herd being BVDV seropositive increased with increasing herd size and increasing titres to N. caninum. The benchmarking of bovid exposure to emerging abortifacient pathogens and identification of their risk factors potentially informs disease prevention strategies, supporting efforts to establish a biosecure beef supply for enhanced smallholder livestock productivity, public health and food security in Laos and surrounding countries.
Highlights
Lao People’s Democratic Republic (Laos) is a low-middle income country of approximately 7 million people located in South-east Asia [1]
These frozen samples were originally derived from the ‘NZ OIE DLF foot-and-mouth disease (FMD) Control Project’ (OIE-DLF) [35] and were collected from October-November of 2016 (n = 235), and a University of Sydney project entitled; ‘Enhancing transboundary livestock disease risk management in Lao PDR’ (ETLDRM) [36] collected from May-June of 2017
To approach the sample size calculated from online epidemiological tools, an additional 47 fresh samples were collected from a buffalo dairy and associated villages in Luang Prabang in February 2018
Summary
Lao People’s Democratic Republic (Laos) is a low-middle income country of approximately 7 million people located in South-east Asia [1]. From 2000 to 2012, cattle and buffalo live weight prices (USD/tonne) increased rapidly by more than 500% and 800%, respectively [1]. Interest in improving large ruminant productivity has been increasing and more recently, enhancing reproductive efficiency is achieving recognition as a valuable opportunity to raise smallholder incomes that may assist alleviation of rural poverty. As Laos is an important livestock trade thoroughfare in South-east Asia, the risk of emerging and transboundary infectious diseases, and foot-and-mouth disease (FMD), increases with the growth of regional livestock trade, threatening attempts to progress livestock productivity [3]
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