The sheep industry in Alberta and elsewhere in Canada has expanded significantly over the past five years. Current mortality losses in Alberta lamb feedlots are very high (4% to 6%) with acute septicemia and pneumonia accounting for 50% of the deaths. The purpose of this project is to identify the causative infectious agents of acute septicemia and pneumonia deaths in Alberta lambs and to develop protective vaccines to reduce morbidity and mortality losses.
Antimicrobials are important to prevent and treat bacterial disease; however, the majority of lambs die acutely of septicemia and pneumonia without any obvious clinical signs of disease prior to death. Thus, efficacious vaccines are needed to prevent disease, improve performance and reduce carcass losses and condemnation. There are no licensed vaccines in North America to control potential infectious agents such as Mannheimia haemolytica, Bibersteinia trehalosi or Mycoplasma ovipneumoniae in sheep
Clostridial spores are found in the soil and are also present in the animals gut. Clostridial diseases can affect animals at all ages depending on the strain, generally the first noticeable clinical symptom is death. Clostridial diseases such as lamb dysentery, pulpy kidney, struck, tetanus, braxy, blackleg and black disease can all be fatal to sheep. Pasteurellosis Pneumonia is one of the biggest killers of sheep in Ireland. The organism that carrys this disease is carried on the tonsils of most sheep and when animals are stressed or run down their immune system is lowered and the disease can take hold.
Vaccination is essential to reducing losses due to these conditions. The Clostridial and Pasteurella vaccines are in-activated vaccines, they won’t recreate the pathogen, and are generally more stable/available than live attenuated vaccines e.g. enzovax, Toxovax. For vaccination to be successful, farmers need to follow manufacturer instructions carefully in terms of product storage and correct administration. An automatic vaccinator gun is recommended as it facilitates the process. Most products are administered via 1 to 2 ml dose given by subcutaneous injection in the loose skin on the upperside of the neck. Cleanliness is essential and it is generally not recommended to conduct vaccinations on sheep with wet fleeces.
Features of Sheep Pneumonia
Control of ovine pasteurellosis is based on four equally important aspects:
Management- Reduction of stress and circulating bacteria can be achieved with careful attention to detail. Significant issues in need of address include ventilation in housing, drainage, mixing of age groups, overcrowding and parasite control. Isolation of clinically affected cases and treating with an appropriate antibiotic can also limit losses.
Biosecurity – Maintaining biosecurity involves avoiding introduction of infected animals into the herd and/or implementing stict isolation / quarantine of introductions until proven negative, and restricting access of livestock to external sources of infection e.g. double fencing is in place at all perimeters.
Vaccination – The use of vaccines confers clinical protection and more importantly reduction of the pathogen circulation. Due to the complex cause of the disease and the fact that clostridia are common killers of sheep, multivalent vaccines are preferred. A number of inactivated vaccines with different combinations of antigens are commercially available. Vaccination programs should start at an early age e.g. from three weeks onwards to protect the young lambs. In situations, where protection is required for more than one winter season, it is advisable to re-vaccinate the animals at least 15 days prior to the risk period. It is critical that a primary course of two doses is administered when beginning vaccination or protection wanes.
For further information on vaccination, please contact your vet. Vaccination with Heptavac P Plus is preferred in breeding sheep as it covers a broader number of antigens while vaccination with Ovivac P Plus may be used in sheep destined for fattening. Ovipast Plus can be used in conjunction with clostridial vaccines to confer protection against Mannheimia haemolytica where a preference exists for broader clostridial cover (e.g. Tribovax 10). Consult your local animal healthcare provider for advice on the correct use of these vaccines.
Treatment – Therapy is limited to the use of antimicrobials and anti-inflammatory drugs. It is often required to start the therapy before results of the bacteriological investigation are available and the resistance patterns are determined. Consequently, the bacteria can exhibit increasing resistance to a large number of antimicrobial agents. Preferably, antimicrobials which are active against Pasteurellae should be used.
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