Hooo-Hooo Hooo-Hooo Volume 12 Issue 01 | Page 4

Coxiellosis in Africa Dr Rick Last – BVSc, M.Med.Vet (Pathology) Specialist Veterinary Pathologist Introduction Coxiella burnetti is a well-documented zoonotic bacterial infection that causes Q fever in humans and coxiellosis in animals. Various domestic and wildlife animal species have been identified as sources of human infection with parturient ruminants being the most common source of disease in man. In animals Coxiella burnetti is clinically associated with reproductive disorders (abortion, infertility), but frequently presents as a subclinical infection, while in man Q fever is characterized by a febrile influenza like illness. Aetiology. Coxiella burnetti is a gram-negative coccobacillus. Classically it was considered a rickettsial agent, but recent phylogenetic analysis suggests that Coxiella burnetti is more closely related to the bacteria Legionella and Francisella. The organism exists in 2 forms namely the large cell variant which is a vegetative form found within infected cells, and the small cell variant which is the extracellular infectious form that is shed in milk, urine and feces and found in high concentrations in placental tissue and birth fluids. The small cell variant is resistant to heat, drying and many common disinfectants and remains viable in the environment weeks to years. Coxiella is considered a potential bioterrorism agent due to its low infectious dose, stability in the environment, ease of aerosol dispersion and ability to cause substantial morbidity in an exposed population. Epidemiology and transmission. Epidemiology is complex with 2 major patterns of transmission occurring. In one the organism circulates between wildlife and their ectoparasites (mainly ticks) while the other occurs in domestic ruminants, independent of the wild animal cycle. Infected ticks may also act as reservoirs of infection. Distribution of the bacteria is worldwide (except New Zealand), with a broad host range including various wild and domestic mammals, arthropods and birds. The greatest risk of transmission occurs at parturition by inhalation, ingestion or direct contact with birth fluids or the placenta of infected animals. The organism may also be shed in milk urine and feces with transmission occurring through consumption of these infected animal products. Ticks are also capable of transmitting the disease amongst animals but are not thought to play an important role in the transmission of disease to people, although rare incidents of tick transmission to man have been reported. Ruminants appear to be the major reservoir of the organism worldwide. Infection is extremely important in small ruminants, particularly goats, where it is primarily associated with abortion or the birth of dead or weak lambs and kids. In Africa camels are emerging as an extremely important source of human infection in certain areas of the continent. In 2014 a one health systematic review into the epidemiology of Coxiella burnetti in Africa, revealed that close contact with camels was associated with increased seropositivity amongst humans. There has been a dramati