Investigation of infectious reproductive pathogens of large ruminants: Are neosporosis, brucellosis, leptospirosis and BVDV of relevance in Lao PDR?

Abstract

<p><i>N. caninum</i>, bovine viral diarrhoea virus, <i>Brucella abortus</i> and <i>Leptospira interrogans</i> serovar Hardjo are globally significant reproductive pathogens that cause abortion and reproductive loss in large ruminants. Prevalence information is lacking in Lao People's Democratic Republic (Laos) despite the poor reproductive performance of cattle and buffalo. Serological examination of frozen cattle (n = 90) and buffalo (n = 61) sera by commercially available enzyme-linked immunosorbent assays provided the first reported screening of some of these pathogens in Laos. Seroprevalence differed amongst these large ruminant species, with <i>N. caninum</i>, BVDV and <i>L. interrogans</i> serovar Hardjo antibodies found in 68.9% (95% CI ± 11.6), 4.9% (95% CI ± 5.4) and 3.3% (95% CI ± 4.5) of buffalo sera, respectively, and in 7.8% (95% CI ± 5.5), 10.0% (95% CI ± 6.2) and 22.2% (95% CI ± 8.6) of cattle sera, respectively. Buffalo sera had a significantly higher seroprevalence of <i>N. caninum</i> compared to cattle (p < 0.001) and cattle sera had a significantly higher seroprevalence of <i>L. interrogans</i> serovar Hardjo compared to buffalo (<i>p =</i> 0.003). Variability was also observed across provinces for <i>N. caninum</i> in buffalo (<i>p =</i> 0.007) and for <i>L. interrogans</i> serovar Hardjo in cattle (<i>p =</i> 0.071), suggesting provincial risk factors conducive to pathogen transmission. BVDV and <i>N. caninum</i> seropositivity were negatively associated in buffalo (<i>p =</i> 0.018) and cattle (<i>p =</i> 0.003). In buffalo, <i>L. interrogans</i> serovar Hardjo and BVDV seropositivity were associated (<i>p =</i> 0.035, <i>p =</i> 0.039). The identification of antibodies against three major abortifacient pathogens in Laos prompts further research to determine if infection is associated with low reproductive efficiency and the risk factors for infection. This is needed for the development of evidence based prevention strategies for improved large ruminant reproductive management among smallholders in Laos.</p>