What You Should Know About Johne’s Disease in Goats
by Jenny Bowles
What is Johne’s Disease? (pronounced "Yo-nees")
Johne’s Disease (Paratuberculosis) is an infectious disease typically identified in wild and domestic four chambered ruminants and it primarily affects the digestive tract. The infection results in a digestive tract that is no longer able to absorb nutrients that are necessary for the body to function with the end result being death. All ruminants are susceptible to the disease and some studies suggest that other animals can become infected. It is non-curative and effective standard preventative vaccines are not available in the
What Causes Johne’s Disease and how does it affect the body?
The disease is caused by the bacteria Mycobacterium paratuberculosis. When the bacteria enters the body, and then to the ileum of the digestive tract, a layer of M cells that are attached to the peyer’s patches, brings the M.paratuberculosis bacteria into the peyer’s patches. Macrophages engulf the invading bacteria in attempt to destroy it, but the attempt fails, the bacteria multiplies inside the macrophage and eventually kills the cell and then spreads to other nearby cells and organs. The animal’s immune system responds to the infection by sending more macrophages and lymphocytes to the infecting bacteria. The prolific infiltration of the millions of macrophafes and lymmphoctes and their reactions causes visible thickening of the digestive walls. The thickening is what leads to the inability to absorb nutrients which results in starvation and death.
Animals typically ingest the bacteria and become infected before they are six months old. The bacteria is very slow growing and can have prolonged dormancy in the animal, which means that the animal may not show clinical signs until it is between the ages of 2-3 years old. Clinical disease is thought to be brought on by a stress factor, such as parturition or introduction into a new herd.
Picture of emaciated goat with Johne's Disease(4)
How is Johne’s Disease Transmitted?
The primary mode of transmission is fecal-oral. Little research is documented in goats about Johne’s disease, but it is also thought that transmission can also occur in utero resulting in kids from an infected dam being born with the disease and possibly from colostrum and milk. M.paratuberculosis bacteria can survive on the ground for approximately one year.
Clinically infected animals shed the bacteria in their manure which leads to susceptible animals ingesting the bacteria. Infected goats can appear to be healthy for a length of time, typically 2-3 years, before the goat becomes clinically ill. For this reason, the bacteria can be shed and ingested by other goats on the pasture, in feeding areas and on dams’ udders before the producer realizes the disease is a problem in the herd.
What Clinical Signs are associated with Johne’s Disease?
Johne’s Disease typically presents as a slow progression of weight loss lasting from weeks to months. Infected animals will often have a very healthy appetite and eventually appear to be starved despite a plentiful ration. The feces generally stay in normal pellet shape, unlike cows which often present with diarrhea. Other signs that may present include anemia, bottle jaw, low grade fever, dehydration, emaciation, general malaise and depression.
How is Johne’s Disease diagnosed and what do the results tell the producer?
Diagnosis methods include bacterial culture of feces to identify the bacteria being shed in the feces and the ELISA and AGID serology tests. The blood tests identify goats that have built anti-bodies to the bacteria. The fecal test identifies if M.paratuberculosis is being shed from the animal. The accuracy and sensitivity of each test varies depending on the test used. The herd’s veterinarian can best determine which test(s) to use and can educate the producer of the interpretation of the results.
It is important to note that there are four stages of the infection. Johne’s infection of the goat typically follows the same course.
The Four Stages of Johne's disease in Cattle (1)
Stage I - Silent, subclinical, non-detectable infection - typically this stage occurs in calves and heifers less than two years of age or animals exposed to a small dose of bacteria. There are currently no tests on the market to detect or identify these animals. Eventually, these animals progress to Stage II.
Stage II - Subclinical shedders typically involving older heifers or adults. These animals may appear healthy, but are shedding enough M. paratuberculosis organisms in their manure to be detected on fecal culture. By shedding organisms, these animals are contaminating the environment. Blood testing may or may not be reliable in detecting these animals.
Stage III - Clinical Johne's disease - any animal with advanced infection, which may have been brought on by a period of stress. A loss of weight and a drop in milk production are also common signs. Many of these animals continue to eat, and are positive on serologic tests. Signs may last from a few days to a few weeks before these animals progress on to Stage IV.
Stage IV - Advanced Clinical Johne's Disease - This is the end stage of this disease. Most animals are very thin. Some animals can progress from Stage II to Stage IV in a few weeks. (1)
By the time that the first goat in a herd is diagnosed with Johne’s, several could be infected.
In a cow milking herd of 100 animals, it is suggested that for every 2 cows showing obvious clinical signs, 25-20 other cows are infected. This iceberg phenomenon illustrates the potential impact the disease can have on a herd. Once Johne’s is identified, it is treated as a herd health problem.
How is Johne’s Disease Prevented?
The best way to avoid the disease is by starting a herd of goats from Johne’s tested free herds that have been consecutively tested disease-free for a number of years.
Management also is a key factor for prevention of the disease. Other preventative measures include routine cleaning and disinfection, pasture rotation, avoiding overcrowding and stress, and using feed and water containers that do not allow fecal contamination to help prevent disease and transmission.
Herds that have been in production but have not been tested should implement a routine testing program. Testing once a year is recommended for herds that do not have any indications of the disease in the herd. If an infected animal is found, testing should be completed at bi-annual intervals and a strict multi-facetted control program will need to be introduced. The herd’s veterinarian can consult and determine the best control program for a particular herd.
A typical control program in the
Johne’s control programs in other countries such as Norway and Australia are using a vaccine (ex. Mycopar) that is injected in young kids less than 30 days old which reduces the shedding of the bacteria once the animal is infected. This vaccine causes all animals vaccinated to test positive with blood tests for the disease and creates large subcutaneous masses at the injection site. The vaccine efficiency is controversial but one study in Iowa reports that 81% of veterinarians and 78% of producers indicated it was effective when used (2). Currently in the
Can Johne’s Disease transmit from species to species?
Some research has shown that it is likely that the disease can transmit from cows to goats and vice versa. Wild deer have also been reported to have this disease. Mixing of species and knowledge of deer populations in the area should be considered in a prevention/control program.
Johne’s disease is not fully understood at this time. It has been suggested that Johne’s disease may be zoonotic. Crohn’s disease in humans is a digestive disease that causes similar symptoms that Johne’s causes in animals. We do not know exactly what causes Crohn’s disease but ongoing studies are working to identify any relationship. Because these studies are ongoing, it is suggested that any producer should be aware of the possible zoonosis and take precautions. Some studies suggest that pasteurization does not completely kill the Johne’s bacteria from meat or milk.
Johne’s Prevalence in goat herds in the United States
In 2009, a unit of the U.S. Department of Agriculture (USDA), NAHMS, will be conducting a national goat survey in the US targeting 85.3% of the population of goats. This survey will help determine how nationally prevalent Johne’s disease is in the
In a survey completed by the author of this brochure, lab results of goats tested for Johne’s disease in
In 1996, a survey completed by the USDA-NAHMS reported that 22% of Dairy cow herds were infected with the disease (8). In a Dairy cow 2007 study conducted by the NAHMS, 68.1% of diary herds were infected with the disease (9). These statistics show how the disease gains prevalence within time even under national surveillance and producer awareness.
Johne’s disease in goats traditionally has been known to be a problem in countries such as Norway and Australia. As the trend of goat production has been rising considerably within the last 10 years in the
(1) http://www.ohioagriculture.gov/pubs/divs/anim/curr/johnes.htm, Johne's Disease, Ohio Department of Agriculture, 11/14/08
(2) http://www.vetmed.iastate.edu/animal_owners/animal_health/Johnes/sites/vaccination.asp, Vaccination, Drs. Norman F. Cheville, Charles O. Thoen, and John U. Thomson, 11/13/08
(3) http://www.aphis.usda.gov/vs/ceah/ncahs/nahms/goats/Goat2009_objinfosheet.pdf , APHIS, 11/14/08
(4) http://www.johnes.org/goats/faqs.html, Johne’s Information Center FAQ, Dr. Michael Collins and Dr. Elizabeth Manning, 11/14/08
(5) http://www.cfsph.iastate.edu/Factsheets/pdfs/paratuberculosis.pdf, Paratuberculosis(Johne’s Disease)and Crohn’s Disease, Iowa Stare University, Anna Rovid Spickler, 11/15/08
(7) Kasey Ridge, 11/17/08, USDA-BOAH, 805 Beachway Drive, Ste. 50, Indianapolis, IN 46224.
(8) http://www.johnes.org/zoonotic/index.html, A complex and controversial question: can M. paratuberculosis infect and cause disease in humans?, University of WI, Dr. Michael Collins and Dr. Elizabeth Manning, 11/18/08
(9) http://www.johnesdisease.org/ , Johne’s Information Central, A cooperative effort of the National Institute for Animal Agriculture and USDA, APHIS, Veterinary Services, in association with the National Johne's Working Group & United States Animal Health Association,11/18/08
(10) http://www.agcensus.usda.gov/Publications/2002/Volume_1,_Chapter_2_US_State_Level/st99_2_017_017.pdf,Milk, Goats, 2002 census of Agriculture,
Other References and Further
http://www.mda.state.md.us/animal_health/diseases/johnes.php http://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1004&context=vetscipapers http://www.johnes.org/goats/faqs.html#2 http://www.vdacs.virginia.gov/animals/johnes.shtml http://news.uns.purdue.edu/UNS/html4ever/020719.Wu.johnes.html
Goat Medicine, Mary C. Smith and David M. Sherman, Edition 1