Coxiella burnetii in ticks, livestock, pets and wildlife: A mini-review

Abstract

Coxiella burnetii is a zoonotic bacterium with an obligatory intracellular lifestyle and has a worldwide distribution. Coxiella burnetii is the causative agent of Q fever in humans and coxiellosis in animals. Since its discovery in 1935, it has been shown to infect a wide range of animal species including mammals, birds, reptiles, and arthropods. Coxiella burnetii infection is of public and veterinary health and economic concern due to its potential for rapid spread and highly infectious nature. Livestock are the primary source of C. burnetii infection in most Q fever outbreaks which occurs mainly through inhalation of contaminated particles. Aside from livestock, many cases of Q fever linked to exposure to wildlife. Changes in the dynamics of human-wildlife interactions may lead to an increased potential risk of interspecies transmission and contribute to the emergence/re-emergence of Q fever. Although C. burnetii transmission is mainly airborne, ticks may act as vectors and play an important role in the natural cycle of transmission of coxiellosis among wild vertebrates and livestock. In this review, we aim to compile available information on vectors, domestic, and wild hosts of C. burnetii, and to highlight their potential role as bacterial reservoirs in the transmission of C. burnetii.

Keywords: Coxiella burnetii; Q fever; coxiellosis; livestock; ticks; wildlife.

Figure 1

Transmission routes of Coxiella burnetii. The bacterium is most often transmitted to humans during parturition of animals. It can be transmitted to humans when they directly come into contact with or inhale contaminated dust from infected animals. It can also be transmitted from a tick bite or by ingesting contaminated/unpasteurized milk and dairy products. Among humans, the bacterium can be transmitted through blood transfusion, sexual, nosocomial and vertical transmission. Sheep, cattle, and goats are the most common reservoirs of the organism for human infection, but infected cats and less commonly dogs can also transmit the infection to humans. Ticks also harbor the organism and are thought to maintain transmission to wildlife species. Dogs and cats, and humans can also become infected when they contact (or ingest) wildlife species.