C. burnetii circulates between wild mammals, birds and ticks in natural herds. Ticks (fam. Ixodida, order Acari) are a reservoir and an important vector, although not the main source of infection for farm animals (CVUA Stuttgart). The main infection source is infected afterbirths following miscarriages in sheep and goats. Up to 40 tick species could be identified as vectors for Coxiella. The ticks remain infected for their entire lives and can even pass on the pathogen to their offspring. In Germany, Dermacentor (Dermacentor marginatus) plays an important role in transmissions between domestic and wild animals, but it is no direct source of infection to humans. C. burnetii could also be isolated from lice, flies and other species of mites, in addition to ticks. 

We differentiate between two independent infection cycles: the first is an infection of natural herds with the participation of ticks and wild animals, which could include infections of domestic animals. This infection cycle is related to the presence of specific tick species. A cycle develops between the larvae and nymphs of Dermacentor spp. and rodents, which affects larger hosts (e.g. red deer, foxes, sheep, goats and cattle) in Germany twice a year (March-April and August-September), when there are adult ticks. Spring and summer-autumn time are known as seasonal risk periods in Germany as a result of the adult ticks changing hosts.

The second cycle is an arthropod-independent cycle in domestic animals. The chain of infection among warm-blooded animals is maintained in this cycle without intermediate hosts. Transmission occurs via miscarriage material, excretions and excrement. Transmission via the respiratory system by particulate and droplet aerosols is also possible.

Coxiella could be spread among domestic animals either passively via ticks in their fleece (dark discolouration in the deeper fleece) or actively via an infection. Infected animals can shed the pathogen via secretions and excrement (vaginal fluids, urine, faeces, saliva).

The pathogen spreads throughout the animal’s body using the bloodstream. C. burnetii multiplies in the phagolysosomes of monocytes and macrophages. In cattle, when the pulmonary nodules are the primary centre of infection, this mostly leads to temporary pathogen infestations of the organs. Coxiella also reach the uterus and the bovine’s mammary glands via the bloodstream, where they can settle for several months, without the infected animal displaying any symptoms. The infection is reactivated during pregnancy, and the uterus and mammary glands can house the pathogen for several years. Both organs then produce and shed considerable quantities of the pathogen. Coxiella are discharged intermittingly along with the milk (Gutteo et al. 2007). Birth by-products (e.g. afterbirth, amniotic fluid, lochia, Gutteo et al. 2006) and the contaminated newborns are highly infectious. Dried foetal skin that remains on the pasture land could result in a month-long contamination of the area.

Transmission to Humans

Q fever can be transmitted from animals to humans via direct contact or via the respiratory system when Coxiella-contaminated particulates or aerosols are inhaled (= aerogenic transmission). One classic infection route for animals, but also for humans, is transmission via tick faeces -- e.g. in the wool of infected and non-infected sheep. Contaminated clothing also plays a role in direct transmission. Occupations that come into direct contact with infected animals, such as farmers, veterinary personnel, people working at abattoirs, shepherds, sheep shearers, but also visitors to farms are at risk. Farm visitors should, therefore, be denied access to facilities with infected animals, so the risk of inhaling contaminated particulates is kept to a minimum. C. burnetii-contaminated dust can be carried by the wind and infect people at a distance of several kilometres.

Coxiella burnetii was not only detected in herds affected by Q fever, but was also discovered in unpasteurised milk (Kim et al. 2005, Gutteo et al. 2006, Henning et al. 2007, Gutteo et al. 2007, Rodolakis et al. 2007, Barlow et al. 2008) and products made from unpasteurised milk (e.g. soft cheese, butter), as well as the meat and organs of infected animals. There is evidence of individual cases indicating humans could also face a risk of food-borne infection. However, food-borne infections play a minor role. Unpasteurised milk from infected herds should generally be subjected to heat treatment as a precaution. It is prohibited to pass on unpasteurised milk and milk products from C. burnetii positive livestock to consumers. Pasteurisation will normally destroy the pathogens.

The animals infected are mostly only diseased on a subclinical level. The infection causes miscarriages in sheep, goats and cattle or the newborn lambs are very weak and have low survival rates (Bildfell et al. 2000, Berri et al. 2002, Arricau Bouvery et al. 2003). Coxiella are also responsible for fertility dysfunction in cattle.

The infection shows no symptoms in the majority of infected humans. The disease – only a third of all infected individuals show symptoms – begins about 2-3 weeks following the initial infection, with patients suffering from shivering, headaches and feeling unwell. The infection can vary in terms of severity and length. In most cases, Q fever progresses to pneumonia, accompanied by intense headaches and muscle pains. Its prognosis is positive. Only five percent of the patients are hospitalised. In individual cases in which an acute infection has not been identified, chronic progress can ensue, predominantly endocarditis. The disease is generally diagnosed using a blood test (evidence of specific antibodies).

Specific antibiotics are used to treat Q fever, if required. Pregnant women should be treated with antibiotics until they give birth, if exposure has been confirmed. Chronic progress (endocarditis) requires even longer antibiotic therapy (3 years). The mortality rate from Q fever is below 1 %.

The EU recommends the following medical control measures: treatment with antibiotics and inoculating susceptible animals before their next pregnancy. A French vaccine developed by CEVA (Coxevac) is available for veterinarians. However, the entire batch produced in 2010 was delivered to the Netherlands. A French combined vaccine for Chlamydia and Coxiella (Chlamyvax FQ by Rhone Merieu; Distribution: Merial) is available. Significant improvements in fertility dysfunction, udder health and pneumonia have been observed in vaccinated cattle.

Medical indications for sheep: vaccination to reduce miscarriage levels before the next oestrus period, the vaccination of sheep in Q fever epidemic regions. While the pathogen is not eliminated by the vaccine, the amount of pathogens discharged by infected animals is reduced considerably.

The fight against Q fever in farm animals focuses on preventative measures. However, early identification of infections in farm animals is required to put prevention and combating measures in place. A few important recommendations to identify Q fever outbreaks are looking for possible infection sources (sheep, goats, cattle, fallow deer), the incidence of miscarriages, examine cattle for ticks (tick faeces in the fleece – dark discolouration in the deeper fleece, inflamed skin/scabs where the animal was bitten by a tick; coal dust-like particles in the region between head, neck and withers with denser fleece) and serologic and molecular biological examinations to clarify the infection quantity (titer increase); immune-histochemical methods and microbiological tests (samples: afterbirth, genital smears).

Measures to reduce the spread of pathogens as a result of passive vector function

Tick faeces in the fleece: disinfection in an appropriate facility – it is recommended to ask for help at the local sheep farmers’ association and treatment with acaricide before the next tick infestation season. 

Shearing in closed rooms – breathing protection, hygiene, burning contaminated wool.

Measures to reduce the spread of pathogens as a result of active vector function

Control of newly acquired animals

Moving highly pregnant animals into the mews to give birth: animals should give birth in closed buildings with enough distance to residential buildings.

Administering tetracycline to highly pregnant sheep will reduce the miscarriage rate, but will not eliminate the pathogen from the herd.

Removing the afterbirth: the contamination of the environment with birth products from infected animals should be minimised to prevent the airborne transmission of the pathogen. Afterbirth and stillbirths should be collected in closed, liquid impervious containers and should be disposed of professionally. The containers must be disinfected properly afterwards.

Infected mother animals and newly born lambs may be taken from the mews 14 days after the birth at the earliest.

Professional disinfection of the mews and equipment affected: 10-20% chlorinated lime solution, 1 % Lysol solution or 5 % hydrogen peroxide solution. Regular cleaning of the facilities should not be done with a high pressure jet or steam during the initial stages, as this might cause the pathogen to spread through aerosols.

Dirty bedding and litter, as well as sheep dung from affected mews must be piled up and covered in plastic foil and stored for two years before it can be used to fertilise agricultural areas. It is not recommended to transports animal waste from infected stalls on windy days due to dust formation.

Individuals who spend time in mews with infected animals to shear them or carry out other activities should comply with the usual hygiene requirements (e.g. washing hands repeatedly, wearing protective gloves, separate work clothes) and wear protective masks. Exposure to infectious particulates from the fleece (tick faeces) can be minimised by shearing followed by a treatment for ectoparasites.

Controlled treatment with acaricides in: a) herds which could be infected before the next tick infestation season; and b) herds in known Dermacentor biotopes at the beginning of the Dermacentor infestation period on a yearly basis. Treatment methods with pyrethroids, combing methods with organophosphates, vaccination methods using macrocyclic lactones. It is impossible to eliminate the Q fever pathogen in natural herds completely, as ticks and wild animals are the pathogen’s reservoir. The spread of the pathogen can be reduced considerably (CUVA Stuttgart) by trying to exterminate ticks in the herds affected every year at the beginning of the tick season (February).

Sheep and goat herds should not get closer than 500 m to residential areas.

No outside visitors at locations with increased risk levels.

Dogs and cats should stay away from mews with infected animals.

Measures/recommendations in the Netherlands: monitoring, breeding stop, no expansion, transportation stop etc.