Discussion and conclusions
The present pilot study evaluated the serostatus of five abortifacient pathogens in an intensively managed dairy cattle herd from Al Ain, UAE. As the study herd had a perennial history of abortion, and since the proportion of seropositive animals was only high for C. burnetii , the present survey further assessed if history of abortion was significantly associated with being seropositive for this pathogen. As the present data have shown, the dairy cattle herd that was the subject of the study demonstrated variable serostatus in respect to the five study abortigenic agents. To the author’s knowledge, this is the first time serological evidence is adduced on apparent C. burnetii ,L. Hardjo , N. caninum , and BVDV infections in dairy cattle in the UAE. While anecdotal reports have previously suggested high prevalence of animal brucellosis, it was rather an unexpected finding that all the 350-screened cattle were seronegative to B. abortusantibodies. It is possible that biosecurity measures adopted in response to previous concerns of animal brucellosis in the UAE have been effective. While C. burnetii antibodies have previously been reported in a number of animal species on UAE territory (Afzal et al. 1994; Chaber et al. 2012; Hassan et al. 2018; Lloydet al. 2010), this is the first time research data suggests coxiellosis infection in dairy cattle. As serological evidence ofC. burnetii infection was previously reported in racing dromedary camels (Afzal et al. 1994), a dama gazelle that had aborted (Lloyd et al. 2010), as well as semi-free ranging wild ungulates (Chaber et al. 2012), and sheep and goats (Hassan et al.2018), a complex coxiellosis epidemiology that arguably involves cross-species C. burnetii transmission cannot be ruled out. This can only be clarified by undertaking more comprehensive epidemiological studies in the country.
It is noteworthy that of the five abortigenic agents evaluated in the present pilot study, the proportion of C. burnetii -seropositive cattle was comparatively greater than for the other four agent for which the proportions of seropositive cattle ranged from 0.0%, through to 0.3%, 1.4%, and 1.7% for B. abortus , BVDV, N. caninum , and L. Hardjo respectively. To further evaluate the abortigenic significance of C. burnetti , the Z test of two proportions was applied to the proportion of C. burnetii -seropositive cattle that had history of abortion and seropositive animals that did not have such a history. As it turned out, the data demonstrated there was statistically significant difference between the two groups (Z test of two proportions; p<0.01) further implicating C. burnetii -in causation of abortion in the affected herd. Indeed, while the list of abortigenic agents screened for was not exhaustive, future study protocols will need to further help delineate the role of C. burnetii in bovine abortions in the study region of Al Ain and beyond. Elsewhere, detection of C. burnetti in the foetal membranes and other biological specimens taken from aborted or stillborn foetuses (Agerholm, 2013; Muskens et al. 2012) has been reported. Moreover, C. burnetii was demonstrated in aborting cattle placentitis (Bildfell et al. 2000; Cabassi et al. 2006). It should be noted that the proportions of L. Hardjo , N. caninum and BVDV-seropositive cattle were comparatively lower than forC. burnetii . As the former three organisms are primary abortigenic agents of cattle (Asmare et al. 2018; Delooz et al. 2018; Yildiz et al. 2017), their animal health implications in cattle in the UAE needs to be further investigated. This is more so important since this is the first time they are being reported in the country. Further still, as Leptospir a is also an important zoonotic pathogen (Garshasbi et al. 2018), the potential public health significance of this bacterium should also be evaluated in the UAE.
In summary, the present data warrant additional comprehensive research into bovine abortion in the UAE. In particular, further research focused on delineating the animal and public health implications of C. burnetii infection is urgently needed. By continuing to generate baseline data on infectious causes of bovine abortion, such studies will in future ultimately pave way to more evidence-based disease control and management strategies for bovine abortion in the country. In the meantime, the present data should inform diagnostic investigation protocols whenever investigating cases of bovine abortion in the country.