Q- fever, Biology

Q- fever
Q-fever or query fever is primarily a disease of animals transmitted to human through inhalation. It is also known as Balkan influenza, Abattoir fever or Coxiellosis. It was first recognized as a new clinical entity among the abattoir workers in Brisbane, Australia in 1935. The causative agent is Coxiella burnetii. C. burnetii is an obligate intra-cellular rickettsia.

Epidemiology: Q-fever has a world wild distribution. It has two interacting cycles. One is maintained in wild animals with their ticks (sylvatic cycle) and the other in domestic animals (domestic cycle). The domestic cycle is not dependent on arthropod transmission. Human infections are associated with the second cycle and only very rarely with the first. In nature it is an arthropod-borne disease like other rickettsial diseases. Natural infection occurs in many mammalian species and is transmitted by ticks. In contrast, with man, transmission from ticks is uncommon. Man-to-man transmission is very rare, if it occurs at all.Man becomes infected by inhaling infected droplets or dust contaminated by cattle, sheep or goats. Man may also be infected by the ingestion of raw milk. The disease usually occurs in epidemic form among slaughterhouse workers and sporadically among farmers and veterinarians.The domestic cycle of Q-fever is mainly a zoonosis and animals like cattle, buffaloes,sheep and goats play a major role in the maintenance of C. burnetii. In the arid desert region this role is played by camels.


Tick vectors: The organism has been demonstrated in a large number of species of ticks. The common tick species are Haemaphysalis spinigera, H. turturis, H. Kinneari,Aponoma gervaisi, Rhipicephalus sanguineus, R. haemaphysaloides, Hyalomma intermedia, H. Hussaini and Boophilus microplus.


Clinical features: The incubation period varies between 14 and 21 days. The disease has an acute onset with fever (101oF to 104oF), chills, general malaise, anorexia and myalgia. Forntal headache is a very characteristic symptom. A variable degree of chest pain is also observed. There is hepatomegaly and/or splenomegaly. In endemic areas the disease may remain as an inapparent infection.


Laboratory diagnosis:
The clinical features of Q-fever are not specific. Diagnosis can be made by serological methods, viz. complement fixation and immunofluorescence tests. A definite diagnosis can be established by isolating C. burnetii, however, isolation procedures are dangerous to the laboratory personnel.


Control and prevention:
Q-fever is mainly an occupational disease for the people employed in the veterinary and its allied fields. The preventive measures should, therefore, be mainly directed towards the protection of such people. All cases of pyrexia of unknown origin in the groups of persons working in slaughterhouses, dairies, wool, tanning industries, etc., should be investigated thoroughly and appropriate measures should be taken immediately.


The necropsied infected animals should be disposed of property. The public should be educated about the importance of consuming thoroughly boiled or pasteurized milk and its products. Effective immunization of the people at risk should be undertaken, however, the vaccines remain impractical because of adverse reactions.

Posted Date: 9/20/2012 2:12:26 AM | Location : United States







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