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CASEOUS LYMPHADENITIS IN GOATS
By: John S. Glenn, DVM, Ph.D.
Caseous Lymphadenitis (CLA, Boils, Abscesses) in Goats with supplemental comments about Sheep
1. Cause: bacteria - Corynebacterium pseudotuberculosis (C. ovis)
a. typically the abscesses contain a thick yellow-green pus with little or no odor
b. once organism enters body, can be transported within cells - which protects organism from host's defense mechanisms (i.e. -antibodies); animal is infected for life and may or may not show intermittent clinical signs
c. body builds thick walls around abscesses - which protects organisms from any antibiotics administered to the animal
d. typically sets up housekeeping in lymph nodes and lymphoid tissues - especially superficial lymph nodes around head, chest, flanks; also occurs in lungs, spinal cord, liver, abdominal cavity, kidney, spleen, brain
e. animal may have external boils without having internal boils and vice versa - no way to predict
f. location of boils determines risk of transmission of organism to other animals - all external boils pose a high risk when draining, as do any boils in the lungs - boils in other tissues, while potentially harmful to the animal, probably don't pose a great risk to other animals
g. lots of argument about how long organism can persist in the environment; more important to know how long it poses a practical threat - probably a matter of days if just smeared on surfaces, probably a matter of weeks/months if incorporated in organic material - bottom line is that resting pastures and pens for at least a month (especially in summer) probably reduces potential exposure to a minimum; scraping the top 2-4" of soil from pens and replacing with new sand or dirt will reduce contamination potential
Organisms could theoretically leave infected animals via the following routes:
SKIN: abscesses draining through skin - important!
RESPIRATORY TRACT: coughing, nasal secretions releasing stuff from lung abscesses - important! High density (crowding) fosters transmission by this route.
Urinary Tract: very unlikely to be shedding in urine (would need to have an abscess in the kidney)
Gastrointestinal Tract: reported to be present in the digestive tract but no one has any good data to implicate manure as a significant source of infection - plus goats are so finicky about what they eat - certainly would be a good idea to clean up manure and keep it out of feed bunks but I wouldn't be paranoid about it - would be most concerned about animals that were thin and "wasting" - need to remember that two other major causes of "wasting" are CAE and Johne's
Mammary Gland: there have been reports of shedding in milk if there are abscesses in the udder - risk that offspring could be infected this way (another good reason to pasteurize milk for human consumption)
2. Initial infection of a herd introduced by bringing in infected animals - may have external boils - may not have any external boils but have some internally - may be actively shedding organisms - may be quiescent, but when the animal is stressed by things such as pregnancy, other diseases, nutritional deficiencies, starts shedding
3. Perpetuation within the herd a) infected animals b) environmental contamination of feed, water, and equipment (milking equipment, clipping equipment, feeders, fences) by infected animals (personally I don't think this persists as long as people say - which is to say that with good sanitation you can pretty effectively control this route) c) human hands (touching infected material and then touching another animal or milking without thoroughly washing hands - see comments in Sanitation and Lancing Abscesses section below
4. Other causes of "abscesses" Certainly abscesses can be caused by a wide variety of organisms when they gain entry into the body - through breaks in the skin (splinters, puncture wounds) or via transport in the blood (acidosis, septicemia). However, these abscess usually are warm to the touch and have very watery contents and a foul odor. Occasionally, goats will develop salivary cysts along the jaws. If the contents of these are aspirated, it will contain a perfectly clear, very viscous fluid.
CONTROL - identify INFECTED animals and keep completely separate (housing, feeding) from CLEAN animals - this means no contact (see exceptions below) or sharing of space. Arrange husbandry routine so you work with INFECTED group last (to lessen chances of carrying organisms back to clean group).
MILKING - milk INFECTED group last and then clean-up well. Don't bring any does with draining abscesses into the milking parlor; wear gloves and change them if you touch an abscess - don't ever treat an abscess in the milking parlor
BREEDING - OK to use clean bucks on infected does (but never on a doe with an active abscess, severe coughing or wasting (can use AI on these cases)) - try to minimize any contact time - obviously AI would minimize the risk. - Using an infected buck on clean does probably carries some risk (if buck is shedding organisms) - no evidence to support transmission by semen (would require an abscess in the testicle or associated structures) - might want to consider AI to minimize risk here
HOW TO GROUP ANIMALS
Note 1: while it is true that a wide variety of other organisms can cause the occasional boil, you can't take the chance of missing a true CLA animal - if the boil is from some other cause, you're going to be able to salvage the offspring anyway - see below.
Note 2: There is no point in spending money to test animals in this group - you have adequate evidence to assume they have been infected.
Note 3: Personally I'm not rabid about culling these animals as long as they appear healthy and are productive and you are willing to take the risk they pose to your control/eradication efforts. There is no reason the majority of them can't go ahead and lead a productive life. BUT if there is an animal in this group that you have second thoughts about for some reason, then use this as an excuse to cull them. Always cull animals with chronic weight loss - not only will you eliminate animals that may be shedding boils organisms, but will also get rid of ones with advanced CAE and Johne's Note: 4: The most ruthless approach would be to automatically cull all visible cases, then blood test and cull all positives - retest remainder in a month - keep doing that until you got no more positives on two consecutive tests Note 5: vaccines are discussed below - probably not a good idea to use any boils vaccines in this group of animals - #1, it's too late for them and #2, infected animals seem more prone to have a reaction to the vaccine
2) Depending on number remaining in CLEAN group:
II) Blood Test
A strong response = actively INFECTED
A weak response = exposed at some point - treat as INFECTED
A negative response can mean several things: the animal could be in the incubating stages of the disease and just not have responded yet; the animal might be truly clean; the animal might have been infected and the body has the infection under control (walled off) - having said all that, I'd consider these negative at this point and just keep a close eye on them. If the CLEAN group starts popping up with abscesses, then you might want to test the group again. Test can be done by:
California Animal Health and Food Safety Laboratory System
- requires 0.5 ml of serum (red cells spun down and removed before shipping)
b) There is an ELISA test, which is more readily available than the SHI test. It detects antigens from the organism and indicates exposure at some time. There are many different ELISA tests available and there is lots of variation in them. The ELISA tests best use is to survey a herd to determine whether the infection is present in the herd, versus using it to decide the fate of an individual animal (i.e. - it would be a good test to use on a herd from which you were considering buying replacements). In some of the ELISA tests, there has been concern that the ELISA will cross-react with Johne's Disease (Mycobacterium paratuberculosis) - although you don't want any Johne's Disease in your herd either so maybe it's a moot point. A number of different states offer the test, including the California Veterinary Diagnostic Laboratory System.
An excellent test is available in Canada:
Mann Equitest Inc.
c) Just a few comments about laboratories - it's important to ask around and find a reliable laboratory and then stick with them - each laboratory uses slightly different procedures, uses different cut-off points and has it's own idiosyncrasies - it's important to develop a working relationship with the people so you can call and discuss questionable results with them (if you can't do this, then it's time to change labs) - this business of constantly changing laboratories and submitting samples to different laboratories until you get the answer you want is counterproductive - all you'll do is multiply the errors and confusion
d) This discussion of tests is full of terribly gross generalizations - the reliability and interpretation of all the tests depends a lot on the level of infection in the group of animals, so until you get some baseline data, it's pretty much conjecture as what's the best to use.
e) While it is true that all tests have some false positives, the even more disturbing aspect is that they all have some false negatives - in an eradication program it's the false negatives that really worry you. So the bottom line from an eradication standpoint is that you should feel comfortable about condemning any animal that tests positive but you should always be a little suspicious about animals that test negative (unless they came from a herd that has been thoroughly tested) - see comments above regarding possible reasons for negative tests. f) Personally, if more than a quarter of the herd is infected and ruthless culling isn't practical, I'd skip the testing and go right to using the vaccine. If there are only a few animals infected, then the tests would be helpful in rooting out the few remaining bad actors. The MAJOR disadvantage of going directly to vaccination is that you then can't use the blood tests since you don't now whether the test is reacting to an actual infection or to the vaccination. This is a permanent downside of vaccination for this disease.
g) Regardless of what you do in terms of vaccination, it is critical to constantly observe these animals closely for any signs of abscesses. Certainly if any animals cough a lot or are very thin, it would be worth running the SHI test on them.
So now you have an INFECTED herd and a CLEAN herd. Once an animal goes into the INFECTED herd, it never comes back to the CLEAN one.
d) vaccinate the animals in the CLEAN herd with a CLA vaccine - animals need two shots the first year, followed by annual boosters. Adult does should receive their second shot the first year and their subsequent annual booster a month before kidding, so there will be maximum protection when the kids hit the ground and before they are old enough to respond to the vaccine themselves. Kids should then be vaccinated starting at 10 weeks of age.
i) Colorado Serum makes a vaccine (Case-Bac) but it is not labeled for use in goats (so the company had absolutely no liability if things go sour) - I've never used it, but I hear of mixed reactions by veterinarians, owners, and goats - some people swear by it and say they have never had problems with it in goats and others swear at it and say they will never use it again. It would probably be wise to initially vaccinate only a few animals and see where herd falls. I'm not aware of any studies but my guess is that the variation is due to a combination of goat genetics, possibly differences in organism strains, other organisms present in the animals, rations and other allergens, presence of stressors, karma, and so forth. The bottom line is that you need to proceed cautiously.
ii) Commonwealth Serum Labs makes a vaccine (Glanvac) in Australia that is used in goats and pregnant animals - I worked a lot with this vaccine when I was on sabbatical leave in Australia and was very impressed with it - we've been trying to get it approved for use in this country but the wheels of bureaucracy turn slowly - it is currently available in Canada.
iii) Autogenous vaccines (made from bacteria isolated on your specific ranch) have been used. You want to be certain that you use a reputable company to produce them for you and then try them in a few animals and wait a couple of weeks before you do the rest. There have been some bad wrecks in the past, so you definitely need to proceed cautiously here too.
In general, goats seem to be more sensitive to these vaccines than sheep and there is always some risk of an adverse reaction (anaphylaxis) - so have epinephrine available and observe the animals for about an hour after vaccination. It is not uncommon to end up with a swelling at the site of injection, followed by a lump that may take several months to disappear, as well as temporary lameness and even a drop in milk production.
In spite of the drawbacks mentioned above, vaccination is a critical part of clearing up a problem herd. Vaccination reduces the number of animals that become infected and develop abscesses (thus reducing exposure) and reduces the severity of and shedding by already infected animals - it seems to be especially effective in holding internal abscesses in check. It has NO effect in terms of ridding the animal of established infections - once infected, ALWAYS infected.
To be protective, the vaccines must be given to the animal before the initial exposure. So, the herd won't really be fully protected until every animal present has been vaccinated since they were kids. There is no quick fix for this disease - this is a long-term program - you just have to slog your way out of it over time.
2) progeny of clean animals can be raised by their clean dams (although you lose the benefits of cutting off the transmission of the diseases mentioned above).
3) As mentioned above, vaccinate the clean does before kidding and then start vaccinating the kids at 10 weeks, giving the booster 4 weeks after that, followed by annual boosters.
QUESTIONABLE, VERY VALUABLE GOATS
2) Quarantine animals in a special pen used just for this purpose for thirty days minimum when you bring them home and use both the SHI and ELISA test on them - if they come up positive to either one, return them to the seller or else place them in the INFECTED herd.
SANITATION & LANCING ABSCESSES
Wear disposable gloves whenever you work around the abscesses - the bacteria can infect humans. Abscesses around the jaws and throat often displace the jugular vein so it's probably a good idea to have these lanced by a veterinarian - a severed jugular vein is not something you want to have to deal with!
If you are going to lance an abscess, restrain the animal on some surface that can easily be cleaned (driveway?) if it gets contaminated, get a large plastic garbage bag and put all the contaminated materials and gloves in it.
Preferably burn the materials that have touched the abscess and it's contents.
Flush the abscesses with an iodine solution.
Scrub and disinfect (2 cups Chlorox in a gallon of water is good) any equipment or surfaces contaminated with abscess contents.
When abscesses are healed, the animal can go back into the INFECTED herd.
HEAT-TREATMENT OF COLOSTRUM
PASTEURIZATION OF MILK
b) 63 C (145 F) for 30 minutes
- if I had a small number of does and could maintain a closed herd (used AI), I'd build a program around blood testing
Supplemental Comments About Sheep
A) Transmission: Shearing and the 2-3 week period after shearing are major times when boils transmission occurs because of the cuts inflicted during shearing, the loss of skin protection provided by wool, and the crowding that usually takes place before and after shearing.
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