Seroconversion to Brucella spp. and Toxoplasma gondii in Sheep and Goats in Dohuk Province, Iraq and Its Association with Pregnancy Loss

Abstract

In this study, sera from 240 small ruminants (192 sheep and 48 goats) belonging to 12 farms in Dohuk Province, northern Iraq, were collected on two occasions to investigate the incidence risk of seroconversion to Brucella spp. and Toxoplasma gondii. All selected animals were confirmed pregnant (approximately 2 months pregnant) by ultrasound examination at the time of the first blood collection. A second ultrasound examination and blood sampling were undertaken two months after the initial scanning/sampling. Antibodies to Brucella were tested using the Rose Bengal Test (RBT) and an indirect enzyme-linked immunosorbent assay (iELISA), and the results were interpreted in series. The Latex Agglutination Test (LAT) and an indirect enzyme-linked immunosorbent assay (iELISA) were also used in series to confirm the presence of antibodies to T. gondii. The seroprevalence for Brucella and Toxoplasma increased significantly between the two sampling times (p = 0.0003 and 0.03 in first and second sampling, respectively). The incidence risk of seroconversion to Brucella over the two months was 10.6% (95% CI: 6.9–15.3) and 7.3% (95% CI: 4.3–11.6) for Toxoplasma. Animals that seroconverted to Brucella were 2.9 times more likely to lose their pregnancy (95% CI: 1.6–5.5) than animals that remained seronegative; however, seroconversion to Toxoplasma had no significant impact on loss of pregnancy. This study is the first reported investigation on the association of seroconversion to Brucella and Toxoplasma with the reproductive outcome of pregnant sheep and goats in northern Iraq. Brucellosis and toxoplasmosis continue to negatively impact small ruminants' reproductive performance and compromising food security in Iraq. It is hoped that this study will assist the development of a better-informed economic model to estimate Brucella and Toxoplasma burden in small animals in northern Iraq, and such a model could be used to validate the impact of various potential intervention programs in.

Seroprevalence of Specific Antibodies to Toxoplasma gondii, Neospora caninum, and Brucella spp. in Sheep and Goats in Egypt

“…A study conducted on pregnant ewes in Iraq found that ewes seroconverting to Brucella were 2.9 times more likely to lose their pregnancy than those remaining seronegative. In the same study, seroconverting to T. gondii had no significant impact on the loss of pregnancy [ 52 ]. Similarly, in another region of the world, only about 1.6% of lost lambs were attributed to T. gondii in a prospective cohort study in primiparous ewes from southern Australia, albeit at an overall much lower seroprevalence than in our study [ 53 ].…”

Cost–Benefit Analysis of a Mass Vaccination Strategy to Control Brucellosis in Sheep and Goats in Northern Iraq

“…This analysis focused on impacts arising from loss of pregnancy and reduced milk yield, as these have been reported to be among the most significant outcomes of infection [ 11 , 27 ]. In this study, we populated the cost–benefit analysis model based on integrated data from our previous research on brucellosis in small ruminants in the study area; key model parameters were informed based on a recent cohort study [ 17 ] and a former cross-sectional serological survey carried out by our group in Dohuk [ 13 ].…”

“…Inputs for the economic model ( Table 1 ) were sourced from: (i) a prospective cohort study conducted in Dohuk Governorate, where a sample of pregnant sheep flocks was followed over time to evaluate brucellosis incidence, seroconversion, and outcome of pregnancy [ 17 ]; (ii) a cross-sectional study conducted in Dohuk, which involved a serosurvey of sheep and goats from 72 farms [ 13 ]; and (iii) a questionnaire conducted on the same farms to gather information on production and prices. Where no data were available in the study area, input parameters were extracted from published literature.…”

“…The true prevalence was calculated from the apparent prevalence (AP) of brucellosis in female sheep and goats using RBT and ELISA in series [ 13 ], together with published values about test characteristics (sensitivity (Se) and specificity (Sp)) ( Table 1 ) [ 19 , 20 ]. The attributable risk of pregnancy loss in new (incidence) cases and in existing (prevalence) cases in sheep and goats was 25% and 18%, respectively [ 17 ].…”