TB in Alpacas
A number of incidents of Mycobacterium bovis infection (bTB) in alpaca herds has raised awareness of TB in camelids. This information describes bovine TB in alpacas and the testing procedure to control it. The information applies to all camelids, however the focus is on alpacas because they are the most common species of camelid found in the UK.
Native to South America, alpacas are adapted to living at high altitude and the lower partial pressure of oxygen this implies. As a result they have a much greater reserve of lung capacity, with some estimates suggesting they can lose up to 90% of functional volume before showing clinical signs of lung disease. In addition they resist showing weakness until the last stage of infection so as not to present an obvious target for predators. For this reason alpacas with clinical disease are very often in the terminal stages.
At post mortem it is common for extensive lesions to be identified in the lungs of alpacas with TB. These lesions are also common in the upper respiratory tract and the associated lymph nodes. Tuberculosis lesions in the liver, spleen and mesenteric lymph nodes have also been described in alpacas.
Like infection in other animals, the onset of clinical disease is insidious and signs are non specific for upper respiratory disease. The most common signs are non-specific for upper respiratory disease. The most common signs include changes in temperament (infected animals become quieter), a loss of condition and weight and, occasionally, increased respiratory rate (hyperpnoea). Bouts of coughing may also be detected in an otherwise quiet environment.
Molecular epidemiology and field investigations have identified at least one instance of transmission of infection between two alpacas belonging to different herds. This means purchased animals could bring into a herd and similarly, any temporary visitors, such as stud males, could introduce disease or take disease home with them. It is therefore strongly advised that movements of alpacas between premises are minimised. Similar risks may occur when showing animals, and it is recommended that visiting or newly purchased alpacas are isolated in quarantine facilities for several weeks, even though clinical disease may not be evident. There is currently no statutory control for the identification and movements of camelids, and keepers should be encouraged to keep accurate records of stock movements for general disease control purposes.
The law requires that Animal Health is notified of any suspect cases of bTB in any domestic mammal without delay. Confirmation of disease leads to herd restrictions, and while there is no routine testing programme for alpacas, owners are typically keen to have their animals tested once infection is suspected or confirmed.
Testing is by the single intradermal comparative tuberculin test (SICTT) applied in the posterior axillary region (behind the elbow). Although not fully validated in camelids, the SICTT is the official TB screening method for camelids traded internationally. This test provides reasonable sensitivity and high specificity, i.e. while it will be unlikely to identify all infected animals in a group; it is likely that the animals it identifies as reactors are infected.
Official Veterinarians can be asked to perform private testing for pre-movement or other purposes, but should seek permission from Animal Health beforehand. A test chart for each test must be submitted to the local Animal Health office.
Camelids are not covered by the compensation system for cattle. In England, Defra may however approve an ex gratia payment of £750 for each animal removed for bTB control purposes. As a pre-requisite for receiving compensation, herd owners are required to refrain from treating animals and allow Animal Health to test remaining animals and remove reactors.
(Source: Official Veterinarian June 2010)
|
Species |
1999 |
2000 |
2001 |
2002 |
2003 |
2004 |
2005 |
2006 |
2007 |
2008 |
2009 |
2010* |
|
Alpaca |
0 |
0 |
0 |
0 |
2 |
1 |
0 |
1 |
4 |
13 |
68 |
40 |
|
Llama |
3 |
0 |
0 |
0 |
1 |
0 |
1 |
8 |
16 |
9 |
0 |
0 |
Source: Veterinary Laboratories Agency TB culture database
*Data provided for 2010 is for the period 1 January – September 2010
Official Veterinarian Issue 6 June 2010- Bovine TB in Alpacas
More information can also be found at www.alpacatb.org