What producers can do to prevent introduction and reduce transmission
Slowly progressive illnesses like Caprine Arthritis-Encephalitis (CAE) in goats are major production limiting diseases that can be a source of significant stress and economic loss for farmers.
Once an animal has the CAE virus, it results in a persistent, lifelong infection. Most goats don’t show any symptoms but can be carriers, which means they can transmit the disease to other animals in the herd. There is currently no treatment or vaccine, and the prevalence across Ontario is unknown.
That’s why Ontario Goat has recently partially funded two research projects at the University of Guelph focused on learning more about the disease, its prevalence and how it behaves on Ontario goat farms.
Determining CAE prevalence
A preliminary study of 45 randomly selected Ontario goat herds – 30 dairy goat breeders and 15 meat goat operations – was carried out in 2012 to determine how widespread the CAE virus infection is in the province. Blood samples were taken by herd veterinarians from up to 20 randomly selected goats at each farm and sent to the Animal Health Laboratory (AHL) at the University of Guelph for analysis.
A telephone survey was also carried out with the participating farmers to gather information about their farm management practices and biosecurity protocols, with questions related to general farm information, biosecurity and production management, and producer awareness of CAE symptoms.
The virus was found to be widespread in Ontario goat herds. CAE was found in 80.4 per cent of the 482 goats tested on the dairy goat breeder farms, and in 17 per cent of the 225 tested animals on meat goat operations. Ten herds – seven meat and three dairy – were found to be 100 per cent negative and seven herds – all dairy – were found to be 100 per cent positive for CAE.
Researchers recommend further work using different herds and a larger, more detailed survey with more farms. Currently, the industry standard is to initially test for CAE in kids between four and six months of age, but whether an operation chooses to test kids at four, six or 12 months of age will depend on the level of CAEV in the herd, herd size, cost and how aggressively the producer wants to approach elimination of the infection.
The producer survey showed farmers need to gain a better understanding of management practices that can reduce transmission of CAE, such as grouping animals by age, removing kids from does immediately after birth, carrying out regimented CAE testing and culling positive goats.
Identifying Ontario CAE strains and their behaviour
The goal of the second research project was to determine the genetic makeup of two small ruminant lentiviruses (SRLV) that infect sheep and goats: CAE and Maedi-Visna Virus (MVV). This is to determine which virus strains are circulating in the province, and how they’re evolving and being transmitted. Blood and serum samples were taken by herd veterinarians from naturally infected sheep and goats – 160 goats on eight Ontario goat farms and 300 sheep from 12 sheep operations across the province.
Overall, researchers found greater genetic variability in the goat SRLV strains than in those found in sheep. Although MVV and CAE are no longer seen as separate viral species and transfer of SRLVs from sheep to goats and vice versa has been documented in Europe, no evidence was found in this study of CAE strains in sheep samples and MVV strains in goat samples. A similar study in Quebec had also found a clear separation of sheep and goat SRLVs on farms in that province.
Sequences of sheep SRLV from this study were found to belong to sequence Group A (viruses clustered around MVV isolates from South Africa, Scotland and Iceland). For goats, sequences from this study were found to belong to sequence Group B, which are viruses related to CAE isolate from the United States. Researchers found no evidence of mutation or recombination between the different goat SRLV, but did discover it for sheep.
Preventing introduction and transmission
In affected animals, CAE virus infects cells of the lung, central nervous system, joints and mammary glands. The most common signs of the disease include progressive lameness in adult goats, and joint swelling and neurological symptoms of brain infection in kids two to four months of age. Animals may also develop mastitis – commonly seen as a hard udder – and decreased milk production, chronic coughing, difficulty breathing, and progressive weight loss that can happen outside of other symptoms.
CAE can be shed in milk, feces, blood, saliva and other bodily fluids. Transmission usually happens from doe to kid, but can also occur via direct contact with infected animals and contaminated equipment. The most common method of spread, however, is when kids drink virus-infected goat colostrum and milk from the dam. It is also thought that CAE can be spread through contamination of milking equipment, needles, tattooing tools and breeding with infected bucks.
The following strategies may help minimize the risk of spreading CAE:
- Isolate newborn goat kids from the doe at birth.
- Feed powdered or pasteurized colostrum.
- Rear kids on milk replacer or pasteurized goat or cow milk.
- House goats according to their age – older goats are more likely to shed the virus.
- Use separate equipment for CAE-positive and -negative animals or for different age groups.
If there are goats in your herd that are showing signs of illness or that you suspect may have CAE, it is recommended to implement a series of isolation protocols to prevent spread of the disease to the rest of your animals:
- Isolate sick animals from the rest of the herd.
- Separate newborns from does immediately following birth to avoid transfer of pathogens from mother to offspring.
- Mixed colostrum or colostrum from unknown CAE status animals should not be fed to negative kids.
- Implement enhanced biosecurity between quarantine areas and the rest of your herd to avoid disease spread.
- Avoid indirect contact with manure or bodily fluids from sick animals. Sanitize tools and equipment after using in sick areas and move into quarantine areas only after you’ve completed work in areas with healthy animals.
- Milk negative animals ahead of positive ones.
- Restrict access to your production areas and keep track of visitors.
- Properly sanitize equipment, especially when moving between negative and positive animals. Ensure negative and positive goats to not eat or drink from the same feed or water sources.
Routine testing and culling of CAE-positive animals, along with testing animals coming into a herd and ensuring breeding stock is negative are also important practices. Producers are encouraged to work with their herd veterinarian to review these strategies and determine herd-specific practices to prevent or reduce the spread of CAE.
More information on the CAE studies is available by contacting Ontario Goat at 1-866-311-6422 or
info@livestockalliance.ca. A movement and isolation checklist for goats is also available.
Written by Lilian Schaer for Ontario Goat.
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