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Vaccination program for pigs

Written by  Dr Joan Kleynhans
| in Veearts
| March 3, 2015

Several infectious diseases threaten commercial pig farming. In this article I will refer to the ones that occur most commonly and should be vaccinated against as part of a basic vaccination program.

The first is Mycoplasma hyopneumoniae

       This organism causes a mild, chronic pneumonia. It is infectious and will produce a persistent dry cough and will also retard growth. Overt respiratory disease will flare up from time to time once it becomes endemic in a herd. Slaughter pigs may show a high incidence of lung lesions. The effects are more pronounced under conditions of overcrowding, poor ventilation and poor husbandry.
        Mycoplasmal pneumonia is often complicated by other mycoplasmas, bacteria and viruses that affect its severity. Within a herd, piglets are infected in the first few weeks of life by their dam or other litters after mixing. Gilts are more likely to transmit the infection to lactating piglets. In cold wet weather, the disease may also be airborne for up to 1.5 km.
        In endemic herds many animals are affected, but there are minimal clinical signs and low mortality. Coughing may commonly be seen when pigs are roused. Weather changes, other stressors, infection or parasites may trigger pneumonia in individual pigs or groups. When the disease first enters a naïve herd, it is usually more severe.  
       Piglets should be vaccinated at the age of one week or older. Vaccine will protect against the development of gross lung lesions and also reduce coughing in growing pigs.

Porcine parvovirus

        This viral disease occurs worldwide and causes abortion in gilts. If they are infected before 70 days of gestation, death of foetuses may result. Not all foetuses are infected simultaneously and typically they die at different stages of pregnancy. Some foetuses may be born alive but are persistently infected.   Typical of the disease is the birth of foetuses of varying sizes, with mummified foetuses and stillborn and live piglets to first parity pigs. Almost all females are naturally infected before their second pregnancy and are then immune for life. Boars shed the virus after infection for a few weeks but semen may be infective. They may introduce the virus into a herd.
        Gilts, sows and boars should be vaccinated five weeks and two weeks prior to breeding.
Erysipelothrix rhusiopathiae
        This bacterium may cause disease in pigs, turkeys and sheep. It occurs worldwide and has been isolated from many species. It may cause localised skin infections and cellulitis in humans working with infected animals or their carcases.
        Asymptomatic carriers are the most common source of infection. It may also be introduced to a commercial piggery by surface water run-off, wild animals, birds, pets and biting insects. The organism can survive in soil for five weeks and for several months in animal tissue such as frozen or chilled pork, cured and smoked ham and feed by-products such as dried blood.
        The organism is resistant to many disinfectants commonly used in piggeries. Bleach and caustic soda will kill the organism. Affected animals may be treated with appropriate antibiotics. Pigs may get the acute septicaemic form of the disease and die suddenly without warning, as seen most often in growing and finishing pigs. In acute infection, pigs are depressed, have a high temperature (40 to 42 degrees C) and are unwilling to stand or move.  If handled, they squeal more than usual.  They may walk stiffly and shift their weight frequently. They are thirsty, won’t eat and will look for damp, cool areas to lie down. The skin is discoloured, often with diamond-shaped pink or purple patches, especially on the back and sides. Their ears, snout and abdomen are often purplish. In untreated cases large areas of skin may slough as well as tips of the ears and tail. Mortality may vary from 0 to 100%.   Pregnant sows may abort. Lactating sows may stop producing milk. Chronically infected animals may develop heart lesions that may cause death. Arthritis may also be a result.
Vaccination against this condition is usually combined with the previous vaccine at five and two weeks before breeding for gilts, sows and boars. Pigs should be vaccinated every six months on an ongoing basis.

Leptospira spp.

        Leptospirosis is an important cause of reproductive failure in swine. Abortions occur one to four weeks after infection. The foetuses are autolyzed. Mummification, maceration, stillbirths and weak piglets may also occur.   Leptospirosis is a zoonotic disease that may affect people, potentially causing very serious illness.
        Combined vaccine, containing porcine parvovirus, E. rhusiopathiae and six species of Leptospira is available and should be given to gilts, sows and boars five and two weeks prior to breeding and thereafter every six months.

E coli and Clostridium perfringens.

        These bacteria cause diarrhoea in young piglets.
        The type C strain of Clostridium perfringens causes fatal bloody enteritis with sudden onset, usually in piglets 1 to 5 days old, though it can affect piglets up to 3 weeks old.
        Enterotoxigenic strains of Escherichia coli cause enteric colibacillosis in nursing and weanling pigs. These pathogenic strains produce enterotoxins, which causes the secretion of fluid and electrolytes into the intestinal lumen, resulting in profuse watery diarrhoea, dehydration and acidosis that often results in death. Rarely pigs may collapse and die before diarrhoea is seen.  
        A vaccine is available which combines these two bacteria. It should be given to gilts five weeks and two weeks before farrowing and to sows two weeks before farrowing if they have been vaccinated before.
        I have discussed the most common diseases one should vaccinate against. There are additional disease control and prevention methods and in some instances treatment with antibiotics and fluids may be indicated. It is advisable to consult a veterinarian about a vaccine and biosecurity program that is best suited to the conditions on your farm.

 


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