Biology Reference
In-Depth Information
interest in this virus, so far as the Indian sub-continent is concerned, arises from
the discovery of this virus in Pakistan in Hy. anatolicum. Moreover, recent investi-
gations have shown that the CHF virus is identical to the Congo virus which was
first isolated in 1956 in Congo and subsequently in many parts of the African conti-
nent, both from humans and ticks particularly Hy. marginatum and Hy. anatolicum.
Hazara virus, isolated in Pakistan from Ixodes redicorzevi, was seen also to be
related to Congo virus. In view of the fact that the Congo/CHF virus produces a
serious typhoid-like illness and is known to be transmitted by ticks, vigilance for
this virus and its vectors in India need utmost attention.
Other Tick-Borne Viruses
42,109
Other tick-borne viruses include Kaisodi from H. spinigera ticks and a bird (ground
thrush), Wadmadani from Hyalomma sp., Nyamanani from paddy birds, Barur from
ticks (H. intermedia) and rodents. Banja virus isolated from H. intermedia ticks of
sheep collected in Orissa state is now known to cause human infection in Yugoslavia.
Dhori virus isolated from Hyalomma dromedarii ticks of camels seems to infect man
in the Western India, on the basis of serologic surveys. Chobar Gorge, a virus isolated
from Ornithodoros sp. in Nepal seems to infect man in the Himalayan region on the
basis of HI results.
Rickettsial Diseases
107,108
The important tick-borne rickettsia diseases in India are “Q” fever and Indian
Tick typhus.
“Q” Fever
The causative agent is Coxiella burnetii. The natural reservoirs include many
kinds of animals. The clinical symptoms are remittent fever, chills, sweating,
anorexia, etc. and can vary considerably in severity. Mortality is about 1%. The
normal mode of transmission appears to be through close contact with the infected
animals, milk, clothing, fecal matter, etc. However, over 40 species of both Ixodid
and Argasid ticks are known to harbor the organisms, but no proved instance of
transmission by bites of ticks is recorded, in nature although vector potentiality of
many species of ticks have been proved experimentally. The incidence of “Q” fever
in India is rather low and perhaps is not reported well.
Tick Typhus
101
Also known as Boutonneuse fever, tick typhus occurs in many parts of India.
The causative agent is Rickettsia conorii and is transmitted by Rhipicephalus san-
guineus, the domestic dog tick in India. But in the African continent, it is transmit-
ted by other ticks such as R. evertsi, H. leachi, and Amblyomma sp. The clinical
symptoms of the disease have been described as fever, headache, and malaise last-
ing about 12
14 days and mortality is low. A maculopapular rash occurs on the
second to fifth day of fever.
Other Tick-Borne Maladies
Apart from being vectors of disease organisms, ticks also play an important role
in ill health in several ways. Tick bites sometimes produce wheals and allergic urti-
caria in sensistized persons. In one instance, a fresh tick bite by H. spinigera was
known to produce allergic reactions at the sites of all previous bites. Paralysis in
