Epidemiology, cost and surveillance of brucellosis in people and livestock of Kyrgyzstan

Brucellosis is a livestock disease which is also transmissible to humans and thus it is of major public health concern. Brucellosis is considered as a major zoonotic disease of public health importance worldwide. However, its prevention and control poses a number of problems to national authorities, particularly to the Veterinary Services and the Public Health sector. The prevalence of brucellosis in Kyrgyzstan is one of the highest worldwide and has been increasing for animals and humans in recent years.
Currently, there is very limited understanding of brucellosis transmission both between livestock species and to humans at the national level. It is important to understand the main transmission routes in order to establish a control strategy of this zoonosis. Brucellosis can ultimately be eliminated only if the disease is controlled in the animal reservoir since animal and human health is inextricably intertwined. It is therefore necessary to consider human and animal health strategies as two aspects of the same aim.
The goal of the current study was to describe the distribution and the transmission dynamics of brucellosis in Kyrgyzstan and to determine its impact on livestock production and public health. The results of the study should contribute to the development of an efficient brucellosis control strategy in Kyrgyzstan.
The specific objectives are: 1) a historical review and analysis of brucellosis control measures used in Kyrgyzstan; 2) a representative sero-survey of brucellosis prevalence for humans and animals; 3) assessment of molecular epidemiology of animal and human brucellosis in Kyrgyzstan; 4) brucellosis cost estimations for livestock owners, brucellosis patients and society; 5) assessment of the potential of abattoirs for brucellosis surveillance; 6) evaluation of the current mass livestock vaccination campaign and promotion of effective brucellosis control in Kyrgyzstan.
This research has been carried out within an interdisciplinary study with the participation of different projects and operational teams involving veterinarians, health workers, epidemiologists, molecular biologists, and laboratory and field veterinary professionals. The study included: serological studies for humans and animals (2006, 2007 and 2012) and the molecular characterisation of Brucella cultures isolated from aborted foetuses of cattle and sheep, (2007-2011) as well as surveillance of abattoirs (2012) and the survey of patients through questionnaires (2013). Based on the collected data, a cross-sector estimation of the societal cost of brucellosis was done. Livestock demographic models were used to estimate the losses in the livestock production. Health provider and patient information was used to estimate the public health costs. Abattoir surveillance was tested for its usefulness to estimate vaccination coverage of brucellosis and the prevalence of PPR.
A national representative cross-sectional study using cluster sampling proportional to size tested a total of 4,936 livestock sera and 1,774 human sera. The overall apparent seroprevalences of brucellosis were 8.8% in humans (95% CI 4.5–16.5), 2.8% (95% CI 1.6–4.9%) in cattle, 3.3% (95% CI 1.5–6.9%) in sheep, and 2.5% (95% CI 1.4–4.5%) in goats (Bonfoh et al., 2012). To confirm the circulating strains of Brucella in Kyrgyzstan, aborted foetuses were collected in Naryn oblast for the strain isolations. Overall, 17 B. melitensis strains were isolated from aborted foetuses of sheep and cattle. Multilocus variable number tandem repeat analysis showed low genetic diversity. Kyrgyz strains seem to be genetically associated with the Eastern Mediterranean group of Brucella global phylogeny. We identified and confirmed transmission of B. melitensis to cattle and a close genetic relationship between B. melitensis strains isolated from sheep sharing the same pasture (Kasymbekov et al., 2013).
We developed a demographic model for livestock and estimated the livestock productivity taking into consideration the real cost of disease and accurate calculations of final losses in the livestock productivity. The losses for Kyrgyzstan were estimated for the period from 2006 to 2011 considering the seroprevalence of brucellosis: 2.8% in cattle, 3.3% - in sheep and 2.5% - in goat.
The societal cost of estimate of brucellosis to Kyrgyzstan includes the cost of public and private health and the livestock production system costs. We developed a demographic model for livestock to estimate cost of disease with and without brucellosis.
Net present cost of brucellosis to the public health sector (2006 – 2011) was estimated at 1.38 million USD (95% CI 1.22–1.55) and the private net present health cost was 6.02 million USD (5.5- 6.5). The overall net present health cost was 23.0% of the societal net present cost of 32.5 million USD (25.7– 39.6). For 2006-2011, losses of the net present value were 13.7 million USD (7.1 – 20.7) for cattle, 0.78 million (0.49 – 2.0705) for sheep and 0.75 million (0.08 – 1.43) for goat products. The incremental asset value was estimated at 2.66, 1.63 and 0.11 million USD for cattle, sheep and goats, respectively. We carried out an abattoir and field study on brucellosis and PPR sero-surveillance. Our finding of field prevalence for brucellosis was in a similar range to the abattoir prevalence. Abattoir prevalence in the area under the study made up 9.8% (95% CI 8.0 -11.5%) and brucellosis seroprevalence in the field studies made up 10.7% (95% CI 8.9 -12.6%). When the abattoir prevalence was adjusted to the national population structure, the brucellosis seroprevalence made up 10.4% (95% CI 8.6 – 12.2%).
However the PPR prevalence was lower in the field when compared to abattoir surveillance. Field surveillance is two times more expensive than abattoir surveillance. For certain cases, abattoir surveillance is feasible and sufficiently accurate when compared with field surveillance.
The abattoir surveillance was predictive for brucellosis field prevalence when adjusted to the national demographic composition but cannot be used to estimate vaccination coverage without good traceability systems at the slaughterhouses.