Tb and camelids
By Linda Blake of Southern Alpacas Stud
Bovine tuberculosis (Tb) is an infectious disease that is a risk to the health of farm animals, human health and New Zealand's export industries. Lifestyle farmers need to be as aware of it as full-time traditional farmers and must meet the requirements for movement of stock.
Alpacas and llamas (camelids) are susceptible to Tb but very rarely get it in New Zealand.
Bovine Tb can infect most warm-blooded mammals. Possums are unusually susceptible to Tb, and possums and ferrets are the main source of infection (or vector) of Tb. In cattle and deer the disease causes small lesions in the lymph nodes of the upper respiratory system and can lead to chronic wasting and eventual death.
Preventing Tb spread
The Animal Health Board (AHB) is responsible for managing Tb in cattle and deer herds, which include compulsory controls on the movement of cattle and deer; testing them for Tb, slaughtering animals which test positive, and control of Tb-infected wildlife populations.
The Alpaca Association of New Zealand (AANZ) has set up a voluntary Tb control scheme for testing and reporting of camelid herd Tb status and all camelid owners are strongly recommended to take part. This is crucial if you or your neighbours have deer or cattle, or you intend to travel your camelids to shows or for matings.
The AHB has classified areas of New Zealand according to the perceived risk of spreading Tb. Areas where Tb is found in wildlife are classified as Tb Vector Risk Areas. Some areas are Movement Control, where stock have to be tested prior to movement out of these areas.
The AHB website www.ahb.org.nz has detailed maps, with a description by geographic or man-made features, of the boundaries. The classification of the area dictates the testing regime that is required. How often you have to test (annually, bi-annually or tri-annually) will be determined by your location, the status of your herd, and, in a movement control area, planned stock movements.
Tb testing for camelids
A dam and her cria wait for their test
to be read. Cria under 6-months are
not tested.
Tb Testing must be done by a qualified tester, like your vet. Testing is done on one day and the test result is read 3 days later - precisely, 72 hours + 6 hours. All animals over six months old must be tested for it to be a whole herd test.
The preferred site is the neck site at the base of the cervical area about level with the animal's back (cranial scapular site). The auxiliary site, behind the front leg, is also acceptable. The fibre is shaved off so the test site is easily seen.
The desired result is a negative test with a swelling of less than 3mm at the test injection site.
A camelid can not be re-tested within 60 days of being tested, as this can result in a "false" positive reaction (to the previous test tuberculin still in their system).
Tb test results
The fibre is shaved off at the
test site, which is usually on
the lower neck.
The single tuberculin test (STT) is used for camelids. This is an injection of "dead" bovine Tb. A swelling of less than 3mm gives "negative" reaction to Tb. If the animal reacts with a larger swelling, it is called a "positive" reaction, as it indicates that there are antibodies for Tb in their system, which may mean that they have Tb.
A comparative tuberculintest (CTT) is generally only used when an animal is being exported or has reacted to a Tb test. This is two injections, one of bovine Tb and one of avian Tb, to compare the reaction and distinguish the type of Tb. Avian Tb is not considered an animal health problem.
Positive results
Usually swelling is checked for by touch. If you get a positive reaction in a camelid, your tester will use callipers to measure the swelling.
The herd will be given a "suspect" status, and certain movements will be restricted until further testing is carried out. An animal that has a positive test result is called a "reactor" and will be tagged with a large ear tag to indicate its status. AANZ and other organisations are notified.
The test is read 3 days later,
initially by feeling for a raised
reaction. Swellings are
measured with callipers.
A second test will be done on the reactor animal - the comparative test. This will distinguish if it has avian or bovine Tb. There are very few camelids who test positive, and generally a second test clears them of bovine Tb.
False positive
If the reactor is proved not to be carrying Tb (a false positive), then the herd returns to its previous status, as if there had not been this incident.
Positive confirming Tb
If a second test on a rector confirms Tb, it has to be put down within 30 days. The whole herd is given a "suspended" status, and certain movements will be restricted until more testing is carried out.
The reactor animal has material cultured from it, and if Tb is present, the whole herd is given an "infected' status and will be placed under movement control measures.
Regular testing of herds which are suspect, suspended, or infected, is carried out until the herd is "clear" again.
Herd status
A herd obtains a herd status. There must be three clear tests within 12 months for your herd to get a Clear status. This is shown by the letter C.
The number of years that a herd has been tested clear (after the initial 3 clear tests) is shown by a number after the C, up to a maximum of 10. For example, Southern Alpacas Stud is C10 - we have been clear for more than 10 years since our initial status testings. We have been whole herd testing for over a decade and we have never had a reactor to bovine Tb in that time.
New animals joining your herd do not affect your status, if they are from a clear herd from a clear area, or have tested negative for Tb. Imported animals from quarantine do not affect your herd status either.
New herds inherit the status of the herd from which the alpacas were obtained. If they come from several herds, then your herd adopts the status of the lowest of the animals.
Moving camelids
Camelids travel for shows and events and for matings, and must abide by the scheme rules. A&P Shows require camelid owners to produce documentation showing they have been tested clear for Tb.
Camelids located in clear vector free areas, with whole herd clear status, can move freely.
Camelids located in vector risk areas, with a clear herd status (whole herd annually tested as clear) can be moved to Shows and clear areas provided the camelid being moved has tested clear for Tb within 60 days of being moved.
If an alpaca from a clear herd in a clear area goes to a vector risk area, for a period of more than overnight, then they can move to another vector risk area freely, but to move back to a clear area they must be Tb tested clear within 60 days of moving.
If you are moving alpacas between different status areas regularly, like females and studs for matings, their movement has to be well thought out and planned in advance. There is an AANZ guideline for Movement of Alpacas for Mating Purposes - check it if you are involved with mobile matings. In Britain a stud llama spread Tb as he visited different farms and spat at resident males.
Note: Please refer to the AHB regulations for moving deer and cattle. The AHB website www.ahb.org.nz has detailed maps, the testing regime that is required, and the procedures and paperwork required for moving cattle and deer.
