Horse Vaccination Protocols |
| Core Vaccines: - Rabies and Tetanus Overview: Rabies and tetanus are both diseases that affect the nervous system. Rabies is a viral infection that is spread in the saliva of infected animals and is inoculated into susceptible animals through skin wounds (often bite wounds inflicted by the animal infected with the disease). Rabies can be transmitted between most mammalian species including humans. Tetanus is caused by Clostridium tetani a bacteria commonly found in soil and manure that causes disease when it enters a low oxygen environment which is commonly found in skin wounds. Objectives: These vaccines are very effective at preventing these diseases and all horses live in environments where the potential for exposure exists. While the threat of exposure to tetanus is more common in horses than rabies; rabies is a disease that can be contracted by people. Horses often have close contact with people; sometimes large numbers of people. This often leads to large numbers of people getting several post-exposure treatments for rabies whenever a case of rabies occurs in horses. For this reason it is equally important that horses be immunized for both of these diseases. Products: -Imrab (must be administered by a veterinarian) Protocols: Foals: vaccinate for both rabies and tetanus at: For foals that are born to unvaccinated mares the passive protection received from the mare will not protect the foal as long nor will it interfere with vaccination as long. Therefore these foals may benefit from vaccination protocols that start at a younger age. The suggested protocols are as follows: Rabies: Tetanus: Adults not vaccinated as foals: The immune systems of mature horses seem to respond fully with fewer initial vaccine doses and so the following initial protocols are shorter. Rabies: Tetanus: Wounded adults: Horses that receive skin wounds are at risk of contracting tetanus. The following are recommended protocols for these horses. Pregnant mares: Vaccinating pregnant mares is intended not only to protect the mare but to improve the passive protection the foal receives in the colostrum against these diseases. The following protocols should be considered. In addition to respiratory disease EHV 1 can cause abortion, weak or stillborn foals and neurological disease. EHV 1 and 4 are in the herpes virus family and are part of a group of viruses that are known for their long periods of dormant infections that periodically flare up into active infections. Therefore horses that have not had contact with other horses for years can become ill with this infection. "Influenza causes acute respiratory signs similar to EHV and while subclinical carriers do occur and can transmit infection this is a situation that lasts for a few weeks and is not life long as in EHV." Strangles is caused by the bacteria Streptococcus equi. In addition to respiratory symptoms more widespread symptoms can occur including abscesses in lymph nodes (usually in the throat) and a bleeding disorder called purpura hemmorhagica that occurs less commonly. The bacteria can be shed for long periods (several months) after the symptoms have completely disappeared. Horses that shed for these time periods complicate control of the disease especially in barns with significant traffic of horses entering and leaving the barn. Objectives: The vaccines available for these diseases are intended to reduce the frequency and severity of illness; not to completely prevent illness. It is not ideal, but it is the limitations of existing vaccine technology and a reduced ability of the immune system to protect the surface of the airways in the respiratory tract compared to the ability to protect the nervous system that is completely contained inside the horse`s body. This is still significant protection compared to non-vaccinated horses and makes a major difference in suffering and death`s during outbreaks. The immunity from these vaccines is relatively short lived and therefore their booster frequency is 6 months to provide optimal protection. The use of these vaccines and the frequency of boosters needs to be based on the risk factors for the disease that are present in the horses activities, age and environment as well as the owner`s ( and perhaps the community of owner`s within the stable) risk tolerance. Products: Foals: Adults with no known vaccinations: - choose the vaccines used based on risk of exposure to influenza, EHV1/4, and strangles For optimal immunization we recommend the following protocol: Pregnant mares: Vaccinating in the face of an outbreak: This is always a controversial practice. If done early in an outbreak with influenza and EHV 1/4, there may be a reduction in the numbers of sick horses and the severity of the symptoms of those that get sick. It may be worth considering using an intranasal modified live influenza vaccine in this situation as protection may occur several days earlier. However, there is a higher incidence of vaccine reactions with strangles vaccines given in the face of an outbreak and some of these can be life threatening. Therefore the use of a strangles vaccine is not recommended in this situation. West Nile Virus, Eastern and Western Equine Encephalitis, and Potomac Horse Fever Overview: This group of diseases are most common in the late summer and early fall. They are transmitted by vectors that are present in warm weather. In the case of West Nile and encephalitis viruses they are transmitted through biting insects. The vector for Potomac Horse Fever is less clear and may be multiple vectors but insects or members of the snail family are the suspects. When West Nile and the encephalitis viruses cause disease, they are usually associated with rapidly progressing nervous system symptoms such as changes in behaviour, weakness, poor co-ordination, and paralysis. Potomac Horse Fever is a digestive system disease that causes watery diarrhoea, fever, and laminitis. These diseases range from uncommon to rare in Ontario. Their frequency even varies within Ontario and from year to year. However, when they do occur the fatality rate is quite high with all of them. The frequency of these diseases is more common in the warmer parts of the United States and this should be taken into account if you travel there with your horse. Objectives: The West Nile and encephalitis vaccines are quite effective and provide high levels of protection against illness. The Potomac vaccines are considerably less effective but do appear to provide a significant reduction in the frequency and severity of disease. Products: Protocols: Foals: Adults with no known vaccinations: give 2 boosters of each vaccine about 1 month apart. Horses that have recovered from West Nile or the Encephalitis most likely will have life long immunity unless their immune system becomes suppressed. These horses may not require immunization to maintain protective immunity unless they do become immune suppressed. Horses that have recovered from Potomac Horse Fever seem to have relatively short immunity and require regular vaccination to maintain even the level of protection this vaccine provides. |