Caprine Arthritus Encephalitis Info Sheet

Veterinary Services
Center for Epidemiology and Animal Health

October 2018

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Caprine Arthritis Encephalitis
Caprine arthritis encephalitis (CAE) is a viral disease of
goats. The virus that causes CAE is one of several small
ruminant lentiviruses in the family Retroviridae.
Retroviruses cause chronic viral infections in many
vertebrate species, e.g., HIV in humans. Infection occurs
when the viral genome is inserted into an animal’s DNA,
producing new viral particles with the host’s cellular
machinery and infecting tissue macrophages, which can
establish infection in multiple organs and evade the
goat’s immune system.. This mechanism allows the virus
to persist for the life of the animal. CAE might cause one
or more of the following clinical signs: arthritis,
pneumonia, mastitis, as well as weight loss in goats and
encephalitis in kids.

Infected animals also lose body condition and
develop a rough coat. In addition, labored breathing due
to pneumonia might be present in mature goats and in
kids. Other clinical signs of CAE include indurative
mastitis, a hardening of the udder caused by an infected
animal’s immune response to the virus. Animals with
indurative mastitis usually have low or nonexistent milk
production. Additionally, weight loss is one of the most
common signs of CAE infection in herds.8

Clinical presentation of arthritis due to CAE infection, causing swollen
knee joints, weight loss, and paralysis of the affected limbs. (photo
credit: Panei, C.J. 2016)

What does encephalitis look like in kids?

Goats test-positive for CAE might appear healthy, and some might
never develop the severe clinical signs attributed to the disease.

What signs indicate a herd might have CAE?
The clinical signs of CAE vary depending on a
variety of factors, including the location of infection, virus
strain, age and condition of the animal and, potentially,
the animal’s genetic background. About 70 percent of
animals with CAE, however, show no clinical signs of
disease, which might be due to low or nonpathogenic
strains of virus.6 Just one or two clinically affected
animals might be the first indication that a herd is
infected, although chronically infected herds might reach
an infection prevalence near 100 percent.6 Arthritis due
to CAE is common in sexually mature goats, and
affected goats become lame over time with varying
severity, but lameness invariably progresses. Distention
at the knee, or carpal joint, is the most classic
presentation of CAE in adult goats.

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Encephalomyelitis is an inflammation of the tissues
in the brain and brain stem and is common in kids 2 to 4
months old. Initially, affected kids will be lame, their gait
will be wobbly and misdirected, and correct placement of
their hind limbs and hooves will become difficult. As the
disease progresses, paralysis of both limbs on one side
of the body, or paralysis of all four limbs, will occur.
Standing will become impossible, so the goats might lie
on their sides and “paddle.” Other signs include
depression, circling, head twitch, head tilt, exaggerated
upward or sideward tilt of the head, and muscle tremors.

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Potential sources of CAE virus transmission
include:9
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Milking machines
Milk buckets
Hands and hand towels
Leaky udders
Estrous mucus
Prepuce mucus
Semen
Saliva and nasal secretions
Colostrum and milk from infected does
Farm and medical equipment such as needles,
tattoo devices, and dehorners

Head pressing is a common behavior in kids affected by
encephalomyelitis caused by the CAE.

How is CAE transmitted among goats?
Consumption of infected colostrum or milk is the
main transmission route of the CAE virus. Other routes
include in utero, kidding (vaginal), saliva and respiratory
secretions from the dam, and cross contamination of
colostrum between does.9 The CAE virus has been
found in cells and tissues along the entire reproductive
tract of does. This finding strongly supports the
possibility of prenatal transmission. The current belief,
however, is that no more than 5 to10 percent of kids are
born with CAE.8
Both symptomatic and asymptomatic animals can
transmit the CAE virus to other animals. The risk of
transmission among high-density goat herds—often
seen in commercial dairies—is higher than in low-density
herds due to the increased stress and contact among
animals in high-density herds. Transmission might occur
through contact with contaminated items or biological
secretions, even when there is not clear evidence of
contamination or infection. Some studies have shown
the incidence of CAE in dairy goat herds is greatest with
high-stocking density; no control measures; deep
manure as the only bedding; feces contamination of feed
and water; frequent introduction of new animals; and
unrestricted use of tattoo, drench, and vaccination tools.7
In addition, the CAE virus has been isolated from the
semen of experimentally and naturally infected bucks.
Therefore, caution should be taken when using natural
or assisted reproduction with semen from seropositive
bucks or from bucks from other producers with unknown
CAE status.

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Transmission of the CAE virus through colostrum and milk is the most
common route of transmission.

Live-animal trade is thought to be a major risk factor
for CAE virus transmission from one herd to another.5, 6, 7
The live-animal trade is also a primary contributor of
disease dispersion in large geographical regions. During
early investigations of CAE virus prevalence in Mexico,
officials found that many infected goats had been
imported from the United States, while Mexico’s
indigenous Criollo goats were not infected.
The CAE virus can also infect other animal species,
in addition to domestic goats. For example, there is
strong evidence that the virus can infect sheep and that
lentiviruses of sheep can naturally infect goats.6
The routes transmission between species include
the ingestion of virus-contaminated colostrum or milk as
well as respiratory secretions from direct contact
between goats and sheep in densely stocked barns.
Producers that raise both species should be aware of
the possibility of interspecies transmission of goat and
sheep lentiviruses. When a control program for one
species is being designed, the mere presence of the
other species and its potential to transmit the infection
should be of utmost importance.2, 6 Evidence of lentivirus
infection has been found in wild ruminants, and
experimental infection with the CAE virus has shown that
these wild species are susceptible to the virus. Although

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lentiviruses of wild ruminants might not currently pose a
threat to domesticated goats and sheep, there is the
potential for cross-species transmission that could lead
to new genetic variants of these viruses. Fortunately, at
this time there is no evidence that CAE is a zoonotic
disease, meaning it will not cause disease in humans
and is not considered a risk to food safety.5

Cross-species transmission of small-ruminant lentiviruses has been
proven in naturally infected animals. This source of disease
transmission could lead to new genetic variants of the CAE virus and
more serious disease in domestic goats (illustration credit: Minardi Da
Cruz, JC. Et al 2013)

What can be done to minimize the transmission
of the CAE virus?
Although vaccines have been developed against the
CAE virus, none has initiated an effective immune
response in tested goats. Therefore, no commercial
vaccines to prevent CAE are currently available.1
The primary underlying basis of CAE control
programs is preventing transmission of the CAE virus
from does to kids, followed by preventing transmission of
the virus among adult goats. A proven way to prevent
virus transmission is preventing kids from nursing
infected does and providing kids with virus-free
colostrum and milk.1 There are a number of
recommended biosecurity practices designed to prevent
transmission among adult goats. Producers that want to
reduce the burden of disease among their animals
should consider implementing the following biosecurity
practices:5
• Strict control of new animals entering property
• Separate newborn kids from their does
• Feed uninfected colostrum, milk, or milk
replacer
• Separate pastures for rearing young goats
• Remove or cull infected animals
• Disinfect animals areas regularly
• Disinfect and temporarily vacate premises in
heavily infected herds
• Conduct diagnostic testing of existing and new
animals

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Efforts to develop accurate and reasonably priced
diagnostic tests for the CEA virus have been intensive.
At least three enzyme-linked immunosorbent assays are
available commercially from U.S. companies. A recent
study found that these three assays have a high
agreement, meaning that they can consistently detect
positive and negative cases.4 These tests, however,
determine if the animal has mounted an immune
response to the virus, but does not indicate the presence
of virus. Therefore, these animals are defined as
seropositive or seronegative, based on the laboratory
results. Virus isolation is used to detect CAE virus
specifically, rather than CAE virus antibodies; however,
using this method in a farm setting is often unpractical.
Producers should consult their local veterinarians about
laboratories that provide diagnostic services for the CAE
virus.
One alternative measure for controlling CAE is
propagating disease-resistant goat breeds. For example,
the disease rarely occurs in some indigenous goat
breeds in European, Middle Eastern, and African
countries, which might indicate that these breeds are
resistant to CAE virus infection.8 These goat breeds,
however, have little contact with imported commercial
breeds, so they might actually be naïve hosts for the
infection, rather than resistant to it. Some studies have
indicated a lower seroprevalence of CAE virus among
Saanen goats in Australia, Golden Guernsey and
Toggenburgs in Great Britain, and Black Boudein goats
in Israel.9 At this time, however, there is minimal
evidence that certain goat breeds are more resistant to
CAE virus infection than other goat breeds, although
future research might identify specific breeds that are
resistant to the infection or to developing clinical of the
disease.

Is CAE infection widespread?
The seroprevalence of the CAE virus ranges from 30
to 80 percent among dairy goat herds in the United
States and Europe. Multiple eradication efforts have
been implemented in European countries. In contrast,
the United States has never implemented a CAE virus
eradication program.1, 2, 5 Eradication in Switzerland
began in 1984 when seroprevalence was 60 to 80
percent. Enforced nationally, the Swiss program has
been extremely successful. In 2017, a national census
using new diagnostic tests revealed that the herd-level
seroprevalence in Switzerland has declined to 0.38
percent.2 Other eradication programs were initiated in
New Zealand, France, and Italy, and all have been
successful.5 The largest challenges to maintaining a
successful CAE virus eradication program have been
financial costs and producer compliance.
While the aforementioned efforts have greatly
reduced the seroprevalence of disease within goat
herds, such efforts are easier to implement and enforce
in smaller countries than in large nations such as the
United States. The best way for producers to control the
prevalence of the CAE virus is to consult their

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veterinarian and implement the previously mentioned
strategies in this information sheet.

How does CAE affect the cost of raising goats?
The pain and disabilities associated with CAE
significantly reduce the quality of life of infected goats;
however, the extent to which the disease might
adversely affect productivity is not clear. In countries
with a high prevalence of CAE virus, animal trade might
be limited, and animals might be culled to control the
disease. Milk production in infected does decreases by
10 to 15 percent compared with noninfected does.5, 8, 9 In
addition, loss of genetic merit could be considered a
major economic loss in high-prevalence herds. Goat
producers should be aware of the increasing consumer
demand for products derived from food animals with
impeccable health statuses.

NAHMS Goat 2019 study
The USDA’s National Animal Health Monitoring
System (NAHMS) will conduct a national study of the
U.S. goat population in 2019. NAHMS collects
management data through surveys to discover potential
strategies for reducing the burden of disease among
U.S. livestock. Producers interested in supporting their
industry are encouraged to participate in the study.
Information on the NAHMS Goat, 2019 study can be
found at http://www.aphis.usda.gov/nahms.

References

1. Michiels, R., Van Mael, E., Quinet, C., et al. Seroprevalence and
risk factors related to small ruminant lentivirus infections in Belgian
sheep and goats. Preventive Veterinary Medicine 2018; 151: 13-20.
2. Thomman, B., Falzon, L.C., Bertoni, G., et al. A census to
determine the prevalence and risk factors for caprine arthritisencephalitis virus and visna/maedi virus in the Swiss goat population.
Preventive Veterinary Medicine 2017; 137:52-58.
3. Panei, C.J., Gos, M.L., Valera, A.R., et al. First isolation and
nucleotide comparison of the gag gene of the caprine arthritis
encephalitis virus circulating in naturally infected goats from
Argentina. Open Veterinary Journal 2017; Vol. 7(1): 32-35.
4. Czopowicz, M., Szalus-Jordanow, O., Mickiewicz, M., et al.
Influence of true within-herd prevalence of small ruminant lentivirus
infection in goats on agreement between serological
immunoenzymatic tests. Preventive Veterinary Medicine 2017; 01675877: 75-80.
5. Tavella, A., Bettini, A., Ceol, M. et al. Achievements of an
eradication programme against caprine arthritis encephalitis virus in
South Tyrol, Italy. Vet Record 2017; 104503:1-5.
6. Minardi Da Cruz JC, Singh DK, Lamara A, et al. Small ruminant
lentiviruses (SRLVs) break the species barrier to acquire new host
range. Viruses 2013; 5:1867–84.
7. Kaba, J., Czopowicz, M., Ganter, M., et al. Risk factors associated
with seropositivity to small ruminant lentiviruses in goat herds.
Research in Veterinary Science 2013; 94:225-227.
8. Iowa State University. Caprine arthritis and encephalitis. 2007.
The Center for Food Security & Public Health.
9. Rowe, J.D.; East, N.E. Risk factors for transmission and methods
of control of caprine arthritis-encephalitis virus infection. In:
Johnson, R.; Pelzer, K. Veterinary Clinics of North America: Food
Animal Practice, v. 13(1), p. 35–53.
10. Crawford, T.B., Adams, D.S., Cheevers, W.P., and Cork, L.C.
Chronic arthritis in goats caused by a retrovirus. Science 1980.
207:4434: 997-999.

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For more information, contact:
USDA:APHIS:VS:CEAH
NRRC Building B, M.S. 2E5
2150 Centre Avenue
Fort Collins, CO 80526-8117
970.494.7000

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