Estimation of the economic impact of a bluetongue serotype 4 outbreak in Tunisia

Introduction

Since 1999, Tunisia has experienced multiple occurrences of Bluetongue (BT) outbreaks, leading to numerous reported cases of infection and mortality in flocks. The re-emergence of the disease in 2020 caused substantial economic losses in cattle, attributed to the incursion of serotype BTV-4.

Methods

To evaluate the economic impact of the recent BT episode, we conducted a retrospective study on outbreaks that occurred in Tunisia between August and November 2020, focusing on the impact at the owner's level and its effects on both small ruminants and cattle. A total of 234 ruminant farms (sheep, cattle, and mixed) were randomly selected across Tunisian governorates and included in the study to estimate both the direct and indirect costs of these outbreaks.

Results

Total costs were calculated as the sum of losses and expenditures resulting from the BT outbreaks. At the animal level, total losses were estimated to range between 116.280 and 207.086 TND for one infected ewe (€33.721 and 60.055). For one lactating cow, costs varied between 2,590.724 and 3,171.107 TND (€751.310 and 919.621). In cattle, exposure to BTV led to a daily unit milk yield decrease of 12.50 to 14.66 L over an average period of 5 months. Diseased sheep experienced weight loss ranging between 4 and 10 kg during the BT outbreaks. The total mean cost of the 2020 BT outbreak in Tunisian investigated farms was estimated at 1,935 million TND (million €561.15) (range: 1,489 and 2,474 million TND; 431.81 and million €717.46). The most influential costs of the total BT outbreaks were the decrease in milk yield, mortality, and veterinary treatment.

Discussion

This study gives valuable insights on the economic impact of the incursion of a new serotype of BT in a naive population in Tunisia. Considering the substantial costs incurred, it is imperative that this disease receives increased attention from stakeholders, including animal owners, veterinary services, practitioners, and decision-makers.

Seroprevalence and associated risk factors of Chlamydia abortus infection in ewes in Tunisia

Enzootic abortion of ewes (EAE) caused by Chlamydia abortus is a disease of ruminants that results in serious economic losses in livestock industry. The zoonotic potential of the pathogen adds a public health concern on the efforts to control the disease. We report herein a cross-sectional study that was conducted during the lambing season (June and July) in Tunisia to estimate the seroprevalence of C. abortus infection in large sheep herds with abortion history. A total of 803 ewes were sampled and tested using indirect enzyme linked immunosorbent assay (iELISA). The overall apparent seroprevalence at herd and individual levels were 58 % (95 %CI = 39-74.5 %) and 6.6 % (95 %CI = 4.9-8.3 %), respectively. Significant risk factors investigated using univariate and multivariate analyses were history of infertility (OR = 5.7; 95 %CI = 3.05-10.66), the number of reproductive ewes (OR = 2.1; 95 %CI = 1.12-3.94), the control of new animals at introduction (OR = 4.35; 95 %CI = 2.46-7.68), the sharing of drinking water (OR = 2.18; 95 %CI = 1.22-3.9), the exchange of breeding males (OR = 2.56; 95 %CI = 1.003-6.54), the disposal of abortion materials without precaution (OR = 4.36; 95 %CI = 2.42-7.87), the lack of lambing barn (OR = 2.39; 95 %CI = 1.13-5.04), the non-application of hygienic post-abortion measures (OR = 10.35; 95 %CI = 5.28-20.26) and the manure management (OR = 11.35; 95 %CI = 3.26-39.48). To the best of our knowledge, this is the first sero-epidemiological survey conducted on an abortive disease in Tunisian ewes that investigated the risk factors of C. abortus infection.