All of following statements are true regarding Q fever except.
Ans. is 'd' i.e. Weil Felix reaction is very useful for diagnosis Q. Fever is caused by a Rickettsia, Coxiella BurnettiCoxiella burnetti is unique to Rickettsia because it has an endospore form. This endospore form confers properties to the bacteria that differ from other Rickettsiae :Resistance to heat and dryingExtracellular existence :- The spores resistance allows extended survival outside a host cell. However like chlamydiae and other Rickettsiae growth and division must occur intracellularly using the host's ATP.Non arthropod transmission: Coxiella burnetti grows in tick and cattles. The spores remains viable in dried tick faeces deposited on cattle hides and in dried cow placentas. These spores are aerosolized and when inhaled cause human disease. So spore inhalation rather than an arthropod bite causes Q fever.Pneumonia: Because the spores are inhaled into the lungs, a mild pneumonia similar to that of a mycoplasma pneumonia (interstitial pneumonia) often develops. Clinical features are :Abrupt onset of fever and soaking sweatsThis is the only rickettsial disease that causes pneumonia and in which there is no rash.Weil Felix is a simple and useful test for the diagnosis of some Rickettsial disease.It is positive in -Epidemic typhus*Endemic typhus*Brill Zinsser disease * (weekly positive)It is negative in -Rickettsial pox*Q. Fever*Trench feverPrinciple of Weil Felix test :Some Rickettsia share antigenic characteristics with certain strains of Proteus Vulgaris (0X19 and 0X2) and proteus mirabilis (OXK). It is purely coincidental that they have the same antigens. Proteus is not involved at all in rickettsial diseases.The Weil Felix reaction is a classic test that uses these cross reacting proteus antigens to help confirm diagnosis of a rickettsial infection.This test is done by mixing the serum of a patient suspected of having a rickettsial disease, with antigens from specific strains of proteus. If the serum has antirickettsial antibodies, latex beads coated with proteus antigens will agglutinate.
It is a zoonotic infection.
Human disease is characterized by an interstitial pneumonia
No rash is seen
Weil Felix reaction is very useful for diagnosis.
Communicable Diseases