Coxiella burnetii  in small ruminants and Q fever in humans

Overview

Coxiella burnetii (C. burnetii) is a bacterium that can pass between animals and humans, and causes Q (Query) fever in humans. It is commonly found in domesticated and wild animals worldwide.

C. burnetii is resistant to heat, drying conditions and many common disinfectants. The bacteria can survive for long periods of time in the environment, including in manure and soil, and may be spread by wind and dust. C. burnetii is resistant to many chemical products. Consult disinfectant labels or veterinary advice to ensure effectiveness against C. burnetii. In milk, the bacteria are destroyed by high temperature pasteurization.

C. burnetii infection in animals

Cattle, sheep and goats are the animals most commonly infected with C. burnetii. Other animals that can be infected include:

• cats
• dogs
• rabbits
• horses
• pigs
• rodents
• wildlife
• birds
• ticks

It is difficult to prevent animals from becoming infected and there are no formal control programs.

Most animals do not show signs of disease. However, infected sheep and goats may abort in late gestation or deliver stillborn or weak offspring. Pregnant cats and dogs infected with the bacteria may also have an abnormal birthing event. Antibiotic treatment of individual animals does not decrease bacterial shedding and has not been proven to prevent further abortions^{footnote 1[1]}.

Bacterial shedding in animal secretions

Infected animals, particularly sheep and goats, shed high numbers of the bacteria in the placenta and birthing fluids at the time of an abortion or normal delivery. Higher numbers of organisms are shed if the birth is abnormal^{footnote 2[2]}. C. burnetii organisms are also shed in the milk, feces, semen and urine, whether after an abnormal birthing event or from infected animals not showings signs of disease. When infected fluids dry out, the spore-like form of the bacteria can survive in the resulting dust for months to years^{footnote 2[2]footnote 3[3]}.

Length of bacterial shedding

Shedding is most prevalent just after birth and tends to decrease afterward, but there are differences between animal species.

Goats

• Vaginal discharge: up to 14 days
• Manure: up to 20 days around kidding
• Milk: intermittently for up to 2 months

Sheep

• Vaginal discharge: up to 71 days
• Manure: up to 8 days after lambing
• Milk: intermittently for up to 2 months

Cattle

• Manure: up to 14 days
• Milk: persistently for up to 13 months

These numbers describe the longest observed times of shedding the bacteria during the follow-up of naturally or experimentally infected herds or flocks^{footnote 3[3]}. Ongoing shedding poses a risk for infection of other animals and people. Producers should consult their veterinarian if abortions or abnormal births are detected.

C. burnetii infections in humans

Q fever is the disease in humans caused by C. burnetii Very few organisms are required to cause infection in a human^{footnote 4[4]footnote 5[5]}.

People usually contract Q fever when they breathe in air contaminated with either:

• the C. burnetii organism from animals aborting or birthing
• dried contaminated materials that become airborne when cleaning the barn or spreading manure

People can also become infected through:

• direct contact between infected materials (for example, tissues, fluids, wool, straw and manure) and skin abrasions or mucous membranes (for example, infected material being splashed into the eye)
• drinking unpasteurized milk

Signs and symptoms of Q fever in humans

Approximately half of people infected with C. burnetii do not develop any signs of illness due to Q fever. Q fever may begin as a sudden illness with flu-like symptoms.

Signs and symptoms can include:

• fever
• headache
• sudden chills or sweats
• muscle pain
• weakness
• nausea, vomiting or diarrhea
• abdominal pain
• chest pain
• non-productive cough

Generally, people become ill 2 to 3 weeks after exposure to the bacteria. The illness usually lasts 1 to 2 weeks and is self-limiting^{footnote 5[5]}.

Chronic Q fever is an uncommon and serious condition that develops in less than 5% of infected people. It may present soon after an acute infection or many years later.

Pregnant women and immunosuppressed persons are at highest risk for chronic Q fever^{footnote 4[4]}. Patients with pre-existing heart valve defects are also at risk because C. burnetii can infect and cause damage to the heart valves.

The antibiotic doxycycline is the first treatment for people with severe illness. People who fully recover from infection may have lifelong immunity against reinfection. Pregnant women infected with C. burnetii may be at risk of miscarriage, pre-term delivery or have low birth weight babies. Refer to your physician if you have health concerns.

More information is available at:

• Public Health Agency of Canada
• Canadian Centre for Occupational Health and Safety
• Appendix 1: Case Definitions and Disease-Specific Information Q fever

Prevalence of C. burnetii and Q fever

In 2009, bulk tank samples from about 28% of Ontario's dairy cow producers and about 95% of the province's goat milk producers were collected and tested for C. burnetii. The herd-level prevalence of C. burnetii in raw cow milk was 62% and 24% in raw goat milk, indicating that C. burnetii is a common finding on Ontario farms. All milk sold in Ontario is pasteurized prior to sale and C. burnetii is inactivated through this process.

A 2013 study of 148 farms in Ontario looked at the proportion of sheep flocks and goat herds that had 1 or more animals test positive for antibodies to C. burnetii^{footnote 6[6]footnote 7[7]}. The detection of antibodies demonstrates these animals had been exposed and had an immune response to C. burnetii. Among the sheep flocks tested, 42% of meat and 64% of dairy sheep flocks tested positive for antibodies to C. burnetii. These results came from testing 50 meat and 22 dairy sheep flocks. Among the goat herds tested, 44% of meat and 79% of dairy goat herds tested positive. These results came from testing 34 meat and 42 dairy goat herds.

The same researchers investigated the C. burnetii seroprevalence among sheep and goat farm workers in Ontario. 67% of the 172 farm workers tested had serological evidence of past infection with C. burnetii^{footnote 8[8]}. Surveillance data shows that between 2012 and 2022, 6 to 20 human cases of Q fever were reported in Ontario per year. This corresponds to a rate of 0.1 per 100,000 people^{footnote 9[9]}.

Risk of contracting Q fever

Workers who have contact with animals, animal products or animal waste are at increased risk to contract Q fever. People at risk include:

• farmers
• farm workers
• veterinarians
• abattoir workers
• shearers
• dairy service providers
• building contractors
• laboratory personnel

Most human infections are linked to contact with cattle, sheep or goats, especially when the animals have recently given birth. Exposure to abnormal animal birth events (abortions, stillbirths, delivery of weak offspring) increases the risk of human infection.

Sheep and goats are more frequently involved in human disease than other animal species, likely because of the higher level of shedding of the bacteria in birth fluids^{footnote 10[10]}. It is possible to be exposed to the bacteria via inhalation at the time of milking, if an infected animal has recently given birth (first 14 days, but possibly up to 28 days)^{footnote 5[5]}.

Less commonly, human infections may be associated with cats, dogs and other animals.

Airborne transmission may occur over longer distances and in some cases may report no known animal contact.

Person to person transmission has been reported rarely^{footnote 5[5]footnote 11[11]}.

Precautions when working with small ruminants

Protective measures should be taken by people working with small ruminants. These include:

• During kidding and lambing, always use disposable gloves and sleeves when handling kids/lambs and birth products. Birthing should occur indoors when possible, out of the wind and in an area that can be thoroughly cleaned and disinfected.
• Wash your hands thoroughly several times a day with an effective disinfectant soap after any contact with animals and before entering the house, handling food or smoking.
• Wash animal manure, urine, milk and other body fluids from equipment and disinfect where practical.
• Keep all protective barn clothing (including hats) in the barn at all times. Clothing should be washed and dried using laundry procedures at high water temperatures.
• Visitors should wear farm coveralls or freshly laundered coveralls, farm boots or disinfected footwear. Visitors and members of the public should not visit ewes or does giving birth.
• Do not consume unpasteurized milk or milk products.
• Pregnant women and those most at risk of Q fever should not assist in lambing or kidding and should avoid contact with sheep and goats during the lambing/kidding season. Other high-risk people include infants and young children, the elderly and those whose immune systems are weakened from poor health.
• Wildlife or pets should not be able to scavenge birth products. Bury and compost or dispose in a closed container.
• Regularly clean and disinfect lambing and kidding areas to prevent accumulation of potentially contaminated materials.
• Maintain a closed herd or flock. Do not purchase, loan or borrow animals. Attending livestock shows and sales may also present a risk to the health of your flock/herd.
• Contact your veterinarian and investigate abortion and stillbirth events.

Vaccines against C. burnetii

A vaccine (Coxevac® CEVA Sante Animale) is licensed for use in cattle, sheep and goats in Europe. Research has shown its use decreased the number of abortions due to C. burnetii and decreased bacterial shedding into the environment. Unexposed replacement breeding stock must be vaccinated annually before breeding^{footnote 1[1]footnote 2[2]}.

Canadian veterinarians may have access to the vaccine through direct application to the distributor for appropriate cases. Producers should talk to their veterinarian about whether the vaccine is appropriate and available for their flock or herd.

There are no vaccines licensed for people in Canada.

What to do if Q fever is suspected in your herd or flock

If you suspect Q fever in your herd or flock you should:

• Take precautions for yourself
  • Wear an N95 respiratory mask type (or higher), gloves and protective clothing when assisting with births and abortions. N95 respiratory mask types must be fitted properly. Contact your local public health unit or a workplace health and safety service for assistance with fitting.
  • If you are concerned about your health, contact your physician or local public health unit to discuss the likelihood of Q fever infection.
• Inform others so they can take precautions
  • Owners must teach their employees about Q fever and provide personal protective equipment.
  • Inform service providers of the risk of disease when C. burnetii is suspected in the herd or flock, particularly when abortions are occurring.
  • Restrict access to the barn containing infected animals, particularly to:
    • children
    • infants
    • pregnant women
    • the elderly
    • those with compromised immune systems
• Take precautions with infected animals and their materials
  • Isolate aborted animals until discharges cease. Restrict access to these isolation areas.
  • Bury or properly compost placentas and aborted fetuses. Do not burn them, as this may increase the risk of aerosol spread.
  • Thoroughly compost manure for at least 90 days before spreading on infected farms. Do not spread manure during windy conditions. Do not spread manure on pastures^{footnote 12[12]}.
  • Consult with your veterinarian to determine an appropriate cleaning and disinfection plan for agricultural areas and equipment.
• Contact your flock/herd veterinarian for more advice on animal control measures to protect animal and human health.

Notify the ministry

In Ontario, veterinary laboratories and veterinarians who use a lab outside of Ontario must notify the Ministry of Agriculture, Food and Agribusiness (OMAFA) following a diagnosis of C. burnetii in livestock. OMAFA will answer any questions the flock or herd veterinarian and producer have regarding C. burnetii and discuss biosecurity practices to limit the spread of disease.

OMAFA will also work with public health officials to assess the risk to people exposed to C. burnetii and encourage them to see their family physician if they have health concerns.

Learn about immediately or periodically notifiable animal health hazards and the requirements for reporting to the Chief Veterinarian for Ontario.