Coxiella burnetii in Humans and Ticks in Rural Senegal

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Q fever in hard and soft ticks

 

Coxiella burnetii in Humans and Ticks in Rural Senegal

 

PLoS Neglected Tropical Diseases 04/12/10

 

_http://www.plosntds.org/article/info%3Adoi%2F10.1371%2Fjournal.pntd.0000654

_ (http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0000654)

 

Author Summary

 

Q fever is a zoonotic disease known since 1937. The disease may be severe,

causing pneumonia, hepatitis and endocarditis. Q fever agent has been

described as a possible biological weapon. Animals—especially domestic cows,

goats and sheep—are considered reservoirs for this infection. They are

capable of sustaining the infection for long periods and excreting viable

bacteria, infecting other animals and, occasionally, humans. Here we studied

the

distribution of Q fever in a poorly studied region, Senegal. We studied the

agent of Q fever both in ticks parasitizing domestic animals and in humans

(antibodies in serum, bacteria in feces, saliva and milk). We found from

the studied regions the bacterium is highly prevalent in rural Senegal. Up to

37.6% of five different and most prevalent tick species may carry the

bacterium. Humans living in such areas, as other mammals, may occasionally

excrete Q fever agent through feces and milk.

Introduction

Q fever is a worldwide zoonotic disease caused by Coxiella burnetii _[1]_

(http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0000654#pntd.0

000654-TissotDupont1) . The disease can be acute or chronic and exhibits a

wide spectrum of clinical manifestations. The reported prevalence of Q

fever is continuously increasing due to both true prevalence and improved

quality of diagnostic tools together with the growing interest of physicians

and epidemiologists focusing on this disease _[2]_

(http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0000654#pntd.0000\

654-Raoult1) . The

natural cycle of this bacterium is not reported to include humans, who are

considered incidental hosts. The true reservoir is wide and includes mammals,

birds and arthropods, mainly ticks. Cattle, sheep and goats are most

commonly identified as sources of human infection and the disease is prevalent

in

mostly rural areas worldwide. Other animals, however, including common

pets such as cats, rabbits, pigeons and dogs _[1]_

(http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0000654#pntd.0000\

654-TissotDupont1)

may also serve as sources. Q fever is usually transmitted by inhalation of

aerosol e1 " >_[4]_

(http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0000654#pntd.0000\

654-Marri[3]</a>. Hard and soft ticks may be infected

during feeding, may transmit <i>C. burnetii</i> transovarially and

transstadially and excrete it <i>via</i> feces, saliva and coxal fluid <a href=)

–_[7]_

(http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0000654#pntd.

0000654-Balashov1) . Being reservoirs, ticks, however, are not considered

as a vector for transmission of this disease to humans, although crushing

an infected tick between the fingers has resulted in Q fever _[8]_

(http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0000654#pntd.0000\

654-Ek

lund1) . Although no human cases of Q fever developing after a tick bite

have yet been reported, the role of ticks as vectors and reservoirs has been

discussed since 1937 _[9]_

(http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0000654#pntd.0000\

654-Derrick1) . The reference strain Nine

Mile was isolated from a Dermacentor andersoni tick and was initially named

Rickettsia diaporica _[10]_

(http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0000654#pntd.0000\

654-Davis1) .

The Q fever agent was subsequently identified either serologically or by

strain isolation in many species of ticks. In the former USSR alone, 32

species of Ixodid ticks, 6 species of Argasid ticks (Ornithodoros tartakovskyi,

O. papillipes, O. alactagalis, Argas persicus, A. reflexus, and A.

vespertilionis) and 5 species of mites were found to harbor C. burnetii _[7]_

(http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0000654#pntd.0000

654-Balashov1) . Coxiella infection in O. moubata was reported once _[11]_

(http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0000654#pntd.

0000654-Weyer2) . Several strains from wild bed bugs (Cimex lenticularis)

were isolated and experimental infection was shown to be stable _[12]_

(http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0000654#pntd.0000\

6

54-Daiter1) .