organisms are frequently absent from fetal tissues.
Abortion occurs in newly exposed animals but may
also occur following repeat infection. Abortion storms
are usually only reported in naïve populations.
Treatment and control.
There is little evidence to support the notion that
antibiotic treatment of animals during an abortion
outbreak provides significant benefit. However,
despite the lack of evidence some practitioners
still advocate the parenteral use of tetracyclines
during abortion outbreaks. Standard abortion
control measures including removal of abortion
materials, segregation of animals by pregnancy
status and diagnostic workup of all abortions should
be implemented in commercial and wildlife farming
operations but application of such protocols can prove
challenging when dealing with free range wildlife.
Zoonotic risk.
Q fever has a far higher incidence in persons who
have occupational contact with high risk species
i.e. veterinarians and livestock farmers (domestic
and wildlife) as well as people who are significantly
immunocompromised. The principal route of
transmission to man is through contact with infected
animal birth products. Clinical presentation in
humans is highly variable ranging from self-limiting
influenza like illness to pneumonia, hepatitis and
endocarditis. This bacterium is highly infectious, and
a single organism reportedly can cause infection by
the aerosol route in man. In conjunction with the high
levels of bacteria in the placenta and birth fluids, this
underlines the importance of taking all the necessary
zoonotic precautions when carrying out abortion
investigations in animals.
Q fever in Africa accounts for a significant proportion
of undifferentiated human febrile illness, pneumonia
and infective endocarditis and in some countries on
the continent, has been reported as a more common
cause of febrile illness in man than malaria.
Conclusions.
Based on the current published data it would
appear that the role of Coxiella burnetti in animals
has been largely under estimated. This is thought
to be in part due to a low level of awareness about
the condition. In addition, the use of serology and
PCR as the primary diagnostic tests, rather than
utilizing histopathology and immunohistochemistry
as the primary investigative tools in animal abortion
investigations, has probably resulted in a significant
number of false negative results. As mentioned
previously up to 20% of infected animals may be
seronegative, while high levels of IgM and IgG are
major inhibitors of the PCR technique.
In certain countries in Africa Q fever is emerging
as a more common cause of severe febrile illness
than malaria and as animals are the primary source
of human infection, the documented incidence in
animals in Africa (based on seroprevalence), are
probably a lot higher than estimated. The role
of wildlife and their ticks in the epidemiology of
coxiellosis and Q fever on the continent currently
remains unknown. African wildlife often have high
tick infestations and therefore can serve as important
reservoirs of many tick borne pathogens for domestic
animals as well as man. In conclusion it would appear
that Coxiella burnetti presents a significant threat to
animal (domestic and wildlife) and human health on
the continent.
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