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.