Seroprevalence and risk factors associated with bovine tuberculosis in cattle in Eastern Bhutan.

Bovine tuberculosis (bTB) is a chronic zoonotic disease affecting cattle of all age groups including wild animals. It poses a significant threat to public health and high economic losses to dairy farmers. While the disease has been eradicated from most of the developed countries through extensive surveillance, testing and culling strategy, it is endemic in Africa, Asia, and the Middle East countries. Currently, there is limited research regarding the prevalence of bTB in cattle in Bhutan. This study aimed to determine the seroprevalence of bTB in cattle in six districts of eastern Bhutan. A two-stage probability proportional to size (PPS) sampling strategy was used to determine the number of animals from which serum samples needed to be collected in each district and sub-district. All farms and cattle for sampling were randomly selected from the data in the annual livestock census of 2020. The samples were tested using bTB ELISA test kit. The seroprevalence and their 95% confidence intervals were calculated. Logistic regression models were constructed to assess the influence of various individual animal and environmental risk factors (breed, age, sex, source of animal, body condition scores of animals, respiratory system status) associated with sero-positivity in animals. The study revealed an apparent seroprevalence of 2.57% (25/971 cattle; 95% CI:1.58-3.57), with an estimated true seroprevalence of 0.91% (95% CI: 0.0-2.81). However, none of the variables were found to be significantly associated with bTB seroprevalence in cattle. We recommend, further sampling and employment of confirmatory testing to fully ascertain the extent of bTB in the cattle herds in eastern Bhutan for prevention and control.

Visual impairment and refractive error in school children in Bhutan: The findings from the Bhutan School Sight Survey (BSSS 2019).

PURPOSE: To estimate the nationwide prevalence of visual impairment and associated refractive error in school children in Bhutan. METHODS: The sample of this prospective cross-sectional national survey comprised of randomly selected classes in levels IV-IX (age 10 to 15 years) from schools throughout Bhutan. The examination included measurement of visual acuity (VA), evaluation of ocular motility, refraction under cycloplegia, examination of the external eye, media and fundus. The principal cause of impairment was determined for eyes with uncorrected VA ≤6/12. The main outcome measures were distance VA and cycloplegic refractive error. RESULTS: With a sampling frame of 1967 class-based clusters from 190 schools, 160 classes in 103 schools were randomly selected; 4985 (98.5%) of 5060 enumerated children were examined. The prevalence of uncorrected, presenting, and best-corrected visual impairment (VA≤6/12) in the better eye was 14.5%, 12.8%, and 0.34%, respectively. Refractive error was the principal cause (94.2%) of impaired vision and 88% of children who could achieve VA ≥6/9 with best correction were without necessary spectacles. The prevalence of myopia (≤ -0.5 D) was 6.64% and was associated with female gender (P = 0.004), urban schooling (P = 0.002), and greater parental education (P<0.001). The prevalence of hyperopia (≥ +2.0 D) was 2.17% and was significantly associated with lower class-level (P = 0.033), and female gender (P = 0.025). The overall prevalence of astigmatism (≥ 0.75 D) was 9.75%. CONCLUSIONS: Reduced vision because of uncorrected refractive error is a public health problem among school-age children in Bhutan. Effective school eye health strategies are needed to eliminate this easily treatable cause of visual impairment.

Changing trends of blindness, visual impairment and cataract surgery in Bhutan: 2009-2018.

PURPOSE: To obtain new rapid assessment of avoidable blindness (RAAB) data on the prevalence, causes and trends of blindness, visual impairment and cataract surgery; and compare the new 2018 data with the older RAAB 2009 data. METHODOLOGY: The second nationwide RAAB used android based mRAAB technique and technology for data collection. Using the compact segment sampling probability proportionate to size, 5,050 participants from 101 clusters of 50 people aged 50 years and older were enrolled through house-to-house visits. Eligible participants received ophthalmic examination and interview by the ophthalmologist-led emuneration team as per the RAAB protocol. RESULTS: The age-sex adjusted magnitude of bilateral blindness in Bhutan was 1.0% (95% Confidence Interval, CI 0.5-1.4) with relatively higher prevalence in rural population (Odds Ratio, OR 1.5, p = 0.13) and women (OR 1.6, p = 0.06). Untreated cataract accounted for the most of blindness (53.8%), severe vision impairment (57.1%), and moderate visual impairment (65.3%); uncorrected refractive error was the main cause of early visual impairment (46.7%). Cataract Surgical Coverage was 86.1% with relatively better coverage in men (76.7% men; 73.1% female) and urban population (79.2% urban; 70.2% rural). Good cataract surgical outcome was achieved in 67.3% and leading cause of poor outcome was ocular comorbidity (43.6%). Accessibility was a significant barrier to the uptake of cataract surgical services. CONCLUSION: There is a 33% reduction in blindness from 1.5% to 1.0%, since the first RAAB survey in 2009. In order to further reduce blindness and visual impairment, Bhutan should continue to implement long-term strategic action plan for eye health focused on strengthening primary eye care and comprehensive eye care service.