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The epidemiology of Brucellosis in sheep, goats and humans in the Iraqi Kurdistan Region

Alshwany, Emad Abdlghafoor Aziz (2019) The epidemiology of Brucellosis in sheep, goats and humans in the Iraqi Kurdistan Region. PhD thesis, Murdoch University.

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Brucellosis is a disease affecting a wide range of domesticated animals and wildlife as well as humans. The disease remains a major zoonotic problem in many regions including the Middle East. In Iraq, where brucellosis is endemic, the disease is a major economic and production limiting disease for livestock owners and the community. Impacts on production arise from reduced milk production, abortions, decreased reproduction rate and premature births. The aim of this project was to investigate the seroprevalence, risk factors and economic impact of brucellosis in sheep and goats in the Kurdistan Region. Also a retrospective study of human brucellosis in Iraq was conducted to describe the historical distribution of the disease and its impact on the population.

Fifty one (39 sheep and 12 goats) of 1,050 sera samples were positive on both an RBT and ELISA (overall seroprevalence of 4.9%; 95%CI 3.6 - 6.3). Although there were no significant differences between groups, the highest seroprevalences were reported in sheep, male animals (sheep and goats) and animals (sheep and goats) older than 6 months compared with goats, female animals and animals younger than 6 months of age, respectively. A multivariable logistic-regression analysis was undertaken to identify risk factors for infection in flocks. This analysis indicated that farmers who introduced (purchased) new sheep (OR: 4.24, 95%CI 1.0, 17.3) and who introduced (purchased) new goats in the 12 months preceding the survey (OR: 15.2, 95%CI 3.0 - 76.36) were significantly more likely to have seropositive flocks. In contrast, flocks that used water sourced from a well (OR: 0.27, 95%CI 0.09 - 0.84) and had goats vaccinated against brucellosis in the 12 month period preceding the survey (OR: 0.31, 95%CI 0.12 - 0.75) were significantly less likely to have seropositive flocks.

Based on the data available, the total economic impact of brucellosis in sheep and goats in 2015 was estimated to be US$6.14 million (95%CI 4.48 - $7.96 million) ($2.56 per adult female) in the Kurdistan Region. By adopting a mass vaccination control program for 10 years the economic losses arising from abortions and decreasing milk production were estimated to decrease to US$1.83 million (95%CI 1.33 - $2.39 million) (US$0.76 per adult female). The median cost of the mass vaccination program over the ten-year period was estimated at US$7.18 million (95%CI 7.11 - $7.25 million) and the total median benefit in present day dollars was estimated at US$18.42 million (95%CI 13.43 - $23.83 million). The abortion rate had the largest effect on the outcome (regression coefficient = 0.74) followed by the prevalence of the disease (0.63).

Based on the official records, the average annual incidence of brucellosis in Iraq, for the period from 1988 to 2002 was 41.88 cases per 100,000 people. There were significant differences between years (overall P value < 0.0001) with the highest annual incidence of 88.2 cases per 100,000 people occurring in 1995. The average annual incidence over this five-year period (2004 to 2008) was 54.11 per 100,000 people in Kurdistan which was significantly higher than the 17.82 per 100,000 people in the rest of Iraq (RR 3.0; 95%CI 1.76 - 5.11). The average annual incidence of brucellosis per 100,000 people for the period 2009 to 2014 in four different provinces of Kurdistan was 36.74. The median cost per patient diagnosed with brucellosis was estimated to be US$321.78 (95%CI 259.53 to $388.72) in the Iraqi Kurdistan region in 2014. The median annual DALYs due to the disease was estimated to be 27.17 (95%CI 15.81 - 42.65) per 100,000 people per year.

It is recommended that to effectively control brucellosis in small ruminants in the Iraq Kurdistan region, an integrated approach should be implemented including adopting risk-based control measures, mass vaccination and education.

Item Type: Thesis (PhD)
Murdoch Affiliation(s): Veterinary Medicine
Supervisor(s): Robertson, Ian, Habib, Ihab and Bruce, Mieghan
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