By: Phillip Sponenberg, DVM, PHD 2009
Abscesses are at least annoying, and can be much more than that to goat breeders and owners. Every abscess must be considered as a potential threat to the herd even though some are fairly harmless.
The reason that abscesses in sheep and goats are important is that many of these are caused by one very specific organism. This disease is called Caseous Lymphadenitis, and the organism causing it is Corynebacterium pseudotuberculosis. This disease is frequently abbreviated as CL or CLA.
The classic course of CL in goats is an abscess in the lymph nodes of head or shoulders. Most of these will be just behind the back of the jaw. They get large, and then rupture with draining of the enclosed pus into the environment. The pus is chock full of organisms, and the environment then becomes contaminated. Usually the pus is thick and pasty, and some breeders insist that they can diagnose this disease on the basis of the pus character. I have seen many of these, and the pus varies from green to white, and from very thick to very watery. I would personally never try to diagnose this on the basis of the type of pus present, for a misdiagnosis has consequences!
The organism of CL lasts in most environments up to 5 months. This is a long time, and is one reason this disease is somewhat difficult to get rid of once it is present on a farm. In addition to its long persistence in the environment, this organism is a very, very specific cause of abscesses. Put another way – most goats that acquire the organism will develop abscesses, so keeping the organism off your farm is a great idea.
These abscesses are not trivial. For starters they are unsightly and indicate disease in the goat. Added to this is that in some goats the organism will cause internal abscesses in lungs or liver, and these will lead to chronic wasting. These abscesses are also important to meat producers, because they can cause condemnation of the carcass.
Due to the very specific link of the CL organism and abscesses, it is important in every case of abscesses to determine if this organism is present or not. This diagnosis can come through a few different means. One of this is direct culture of the abscess content. This is the most reliable, and the organism is easy to grow in culture (contact your vet for this). A second method is serology on blood samples, although this is not as accurate as culture. An advantage, though, is that serology can be used on animals that do not have an active abscess.
If CL is diagnosed in a herd, then the problem quickly becomes what to do about it? For starters, it is at least unethical to sell animals that have CL or are likely to develop it (having originated in an infected herd) without alerting customers that this is a possibility. This is a SERIOUS disease.
To eliminate the disease and the organism, most breeders simply cull animals as they develop abscesses. This process, depending on numbers and facilities, can take as long as two or three years. Remember, the organism lasts in the environment up to 5 months. Add to that the incubation period from infection to abscess, which can be close to two years. The usual course of events if culling and elimination is undertaken is that the number of new cases very quickly declines. After the initial case few more occur, and with increasing time, fewer and fewer until finally no new cases ever occur because the organism is eliminated from the farm.
One of the best strategies for culling is to simply palpate the outside of the goats carefully for lumps about once a month. Pay attention to jaw line, front of shoulder, back of shoulder, front of stifle, and above the back of the udder. That will catch nearly all of them, and can be done quickly.
A second approach is to blood test all in the herd, and eliminate the positive animals. This is likely to proceed quickly at first, although vigilance is still needed because a few can still develop abscesses. The herdwide blood test should probably be repeated every six months until two consecutive tests reveal everyone to be negative.
In some situations breeders may choose to live with the disease, although this is problematic if someone is selling breeding stock. In such a situation it is always wise to limit contamination of the premise, so goats with abscesses should be isolated while draining. The abscesses can be lanced, or can spontaneously rupture, and can then be treated with topical iodine solutions. The goat should be isolated in a restricted environment (remember – the environmental contamination is the issue of importance here!) until the abscess is completely healed.
A second treatment that is occasionally used is surgical removal of the abscess by a veterinarian. This sounds great in theory, but many of these are deep, and many are in the neck – close to things like jugular veins, carotid arteries, and important nerves. Surgery close to those structures is tricky at best!
A third treatment is more controversial, and involves tapping into the abscess with a syringe, draining pus and then introducing formalin into the cavity. This is technically very illegal, because formalin has no withdrawal period. Even though goats may not be intended for meat, all goats fall under meat quality standards – so use of formalin is illegal.
A few important issues arise if goats are treated and allowed to stay in the herd. First is that such goats frequently become repeat offenders. That is – they develop abscesses repeatedly, and commonly in different areas of the body. A few may have a single abscess, recover, and never develop another one. But the very real problem for the owner of a goat with a CL abscess is that it is impossible to tell if any individual goat will be the one that heals and never recurs, or the one that has a new abscess (external or internal) every six months from now on.
A vaccine has been developed for use in sheep, and some breeders have had success with this in goats. Using it might alter the blood test results, but the vaccine has been used effectively to reduce and then eliminate the organism in some infected herds. Remember – all you really have to do is eliminate the abscesses and the shedding to eventually eliminate the disease. So, those who use the vaccine are constantly imparting resistance to the goats, so that fewer and fewer develop abscesses.
Experiences with the vaccine vary considerably. It is generally safe, but if goats that are already infected are vaccinated then some of them will develop an immense and painful reaction to the vaccine. This usually takes 12 hours or so to develop, and these goats will develop massive swelling, pain, and fever associated with the vaccine site. As a result, some breeders with a CL problem only vaccinate the kids, since they are the least likely to be infected and to come down with the reaction.
A summary of CL is:
- It is an important disease
- Anyone selling goats (especially breeding stock) should be free of it.
- Ways to be rid of it vary – but never having it to begin with is the very best way to never have it.
- Culling is usually the quickest way to be rid of it.
- Treatment of abscesses can slow the progression – no CL abscess should be allowed to drain into the environment. This strategy decreases environmental contamination, and therefore new cases.
- Vaccination can decrease the incidence of new cases so that few develop. Over a period of years it can eliminate the organism from the herd, especially if the original offenders are identified and eventually culled or isolated.
And, at last, not all abscesses are CL. This is important, because eliminating the CL organism will not necessarily eliminate all abscesses. These “nonCL” abscesses can be caused by a host of organisms, but none of them is as specific as the organism causing CL. What this means is that infection with these others may or many not cause an abscess, these organisms tend to not be specific for goats, and they usually don’t last long in the environment. So – they are not a big threat to the herd. Especially in a CL negative herd, though, any abscess needs to be documented as being “not CL” so that the non-CL status is verified for both owner and customers.
The way to assure that an abscess is one of these others rather than CL is to culture the abscess. I have very few abscesses in my herd, usually one every two or three years (out of over 100 goats). I culture these, simply to document that they are NOT CL (which I don’t have and don’t need). I have had goats with Streptococcus, Archanobacterium, and Pasteurella abscesses. In each case the abscess was drained and treated topically – and the herd remains safe in its CL-negative status.
However – if I ever do culture the CL organism from an abscess, you can be assured that this animal would have to go away, and that the rest of the herd would have monthly external exams. This is not a disease to toy with, and all goat producers should be diligent to eliminate it.
