Jayasekara, Preethinie Punyakumari

Walkden-Brown, Stephen W

Freitas Gerber, Priscilla

Olmo, Luisa

Jenkins, Cheryl

2025-03-25

<p>The popularity of goat farming in Lao PDR is constrained by diseases. Information on the type and prevalence of diseases in Lao goats is scattered in both the formal and informal literature, and the actual causes of common clinical syndromes are not known definitively. The situation is exacerbated by a lack of veterinary and extension services in rural areas and clear control strategies. Therefore, the work reported in this thesis was designed with four broad objectives: 1) collate the disparate data on diseases of Lao goats within the context of goat production, marketing systems and the available veterinary services in the country; 2) determine animal-level and herd-level prevalence of common clinical syndromes in Lao goats, to determine risk factors for herd-level occurrence of the most prevalent clinical syndromes; 3) determine causation for important clinical syndromes of goats in Lao PDR (eye infection, proliferative lip and facial lesions and respiratory disease) and pathogen genetic relatedness by conducting phylogenetic analysis; and 4) introduce and establish molecular diagnostic methods relevant to most common goat diseases at the Lao National Animal Health Laboratory (NAHL). Initially a review of the existing literature on goat diseases in Lao PDR was conducted to collate scattered data in the formal and informal literature. Secondly, a monthly survey based on the observations of smallholder goat farmers was conducted over 22 months to identify the prevalence of clinical syndromes and associated risk factors. Then a case-control study was conducted using PCR-based diagnostics and sequencing to identify causative infectious agents for three of the clinical syndromes in Lao goats. Lip and mouth lesions (presented on 12.2% of monthly visits), diarrhoea (9.3%) and eye lesions (9%) were the most prevalent syndromes based on farmer observations. Occurrence of any type of clinical syndrome and eye lesions were positively associated with increasing herd size and provision of salt respectively. The case-control study was used to determine the causation of eye infection, proliferative lip and facial lesions and respiratory disease, but not diarrhoea due to the unavailability of adequate number of samples. The case-control study involved 41 – 50 samples from cases and the same number from matched controls for each syndrome. The main cause of eye infections was infectious keratoconjunctivitis (pinkeye) caused by <i>Mycoplasma conjunctivae</i>. The main cause of proliferative lip and facial lesions was orf (contagious ecthyma, scabby mouth) caused by the orf virus. The main cause of the chronic respiratory syndrome was atypical pneumonia caused by <i>Mycoplasma ovipneumoniae</i>. These provided the first definitive determination of causation of three important clinical syndromes in Lao goats. The findings of this thesis have important implications for improved disease diagnosis, control and future research to support Lao goat production.</p>

https://hdl.handle.net/1959.11/69191

en

University of New England

Causation and improved epidemiological understanding of major clinical syndromes constraining goat production in Lao PDR

Thesis Doctoral

Publication