1. DISEASES OF PIGS
Two types of pigs are normally kept on farms, those that are being reared to sell as meat and those kept for breeding. The majority of pigs are sold as meat and they are kept during the period of rapid growth. These pigs are killed before they have stopped growing and most of their problems are the illnesses associated with rearing. With breeding pigs, the main problems are infertility and the diseases associated with sows farrowing (giving birth) and rearing their litter.
However, there are some diseases that affect pigs of all ages.
Many pigs illnesses can be prevented through good management, and placing the following points into practice:
- Good housing which shelters the pigs from rain and wind but which allows them plenty of fresh air;
- Keeping the pigs warm in winter and cool in summer. Pigs are not covered in hair the way other animals are and they suffer if they are too cold or too hot if they have no shelter from the sun;
- Feeding properly balanced rations to the different classes of pigs on the farm. Pigs must receive the correct amounts of carbohydrate, protein, minerals and vitamins for their size and weight and they must have access to clean water at all times; and
- Keeping the pigs clean by cleaning out their pens every day and giving them fresh litter in the form of straw, stover or sawdust. Pigs are by nature clean animals and will defecate in the part of their pen away from the sleeping area. Regular daily cleaning will keep them free from lice and mange and will reduce the flies in the piggery.
2. MAJOR DISEASES THAT AFFECT ALL PIGS
This disease is covered in Lecture 5, and, if the disease is suspected, the Department of Veterinary Services must be notified. Never carry out a post mortem on any animal if you suspect it has died of anthrax because man can be infected with the disease easily.
FOOT AND MOUTH DISEASE
This has been covered in Lecture 4 and the disease must be reported to the Department of Veterinary Services. Animals can be protected by vaccination with the correct strain of the virus.
A highly infectious disease of pigs which is caused by a virus of which there are a number of different strains.
The live virus has been found after 1 month in smoked and salted pork, after 2 months in the bones of smoked and salted pork and after 4½ years in frozen pork, but the virus is killed by boiling and by disinfectants. In many countries it is law that all swill fed to pigs must be boiled.
The disease is spread by infected pigs or infected pig products, and it can be carried by birds, on clothes, or by cars and lorries, especially on the tyres. Once a pig has had the disease and has recovered, it is immune for life, and a passive immunity can be transferred from a sow to her piglets through the colostrum.
The incubation period is from 3 to 6 days but in some cases may be much longer. In acute cases animals are found dead, but in other cases the pigs will develop a high temperature with fever spreading very rapidly through the herd. Affected animals appear listless and show a catarrhal discharge from the eyes and sometimes the nose. As the disease develops, the animals suffer from severe diarrhoea and blotches appear on the skin, death occurs within 1 week.
Swine fever is difficult to diagnose because the symptoms are very similar to other diseases such as Salmonella and Erysipelas. Once the disease has spread through the animal, no treatment is effective.
The disease can be controlled by a vaccination programme, with the careful selection of vaccine according to the strain of the virus, or by use of a slaughter policy.
This is used in the U.K. where all pigs with the disease, together with those pigs in contact with infected animals, are slaughtered and the carcasses burned on the farm. The farm is placed in quarantine and all the piggeries, vehicles and clothes of the stockmen are thoroughly disinfected. Pig markets in the area are closed and the movement of pigs is forbidden. This policy can only be enforced by legislation.
AFRICAN SWINE FEVER
Is caused by a virus and affects domestic pigs, wild pigs and wart hogs in Africa. It is spread by feeding unboiled, contaminated swill to pigs, by direct contact with an infected domestic or wild pig or by a tick bite. The symptoms are similar to those of Swine Fever, and infected animals usually die. There is no treatment or effective vaccine, and the disease must be prevented by always boiling swill before feeding it to pigs, and by preventing any contact between domestic pigs and wild pigs or wart hogs roaming in the bush. In the case of an outbreak, the best policy is to slaughter all pigs in the area, disinfect thoroughly, and allow a period of at least 4 months before re-stocking.
Is caused by a virus that affects pigs mainly between 3 and 18 months old, although older pigs can be infected. Some pigs are carriers of the disease and infect the soil in grazing areas through contaminated faeces. The bacteria are passed on to other pigs feeding in the same area, through food, cuts and scratches on the pigs or through flies. The disease can be acute or chronic. In the acute form the animal has a high temperature, a discharge from the eyes, the skin on the abdomen becomes dark red and the animal usually dies. In the chronic form the animal develops stiff joints and characteristic diamond shaped, dark red patches on the skin. The disease can be treated with injections of penicillin, but animals that recover should be sent for slaughter as they do not thrive. Control of the disease is difficult, the main precaution being to make sure that pigs brought into a pig unit are not carriers. Vaccinations are available but their effectiveness is variable.
Pigs are very susceptible to sunburn and heatstroke and should always have shade from direct sunlight. Heatstroke can be caused by direct sunlight or by bad ventilation and overcrowding in a pen. Affected pigs appear to be greatly distressed, have a very high temperature, as high as 44°C, and seem half paralysed. Death can occur very rapidly. Treatment is to move the pig to a cool, shaded place and douche it with cold water until the temperature falls to normal. Spraying the animal all over with a garden hosepipe is a good method of applying the cold water.
All pigs and particularly breeding stock are susceptible to attack by mange mites which burrow into the skin and cause itching. Secondary infections can enter the raw patches on the skin caused by the animal’s rubbing and scratching. Treatment is by washing the animal with a proprietary remedy and all sows should be treated a week before they are due to farrow so that the mites do not infest the newly-born piglets.
Pigs of all ages can suffer from infestation by roundworms (Nematodes) and tapeworms (Taenia solium). All pigs should be dosed regularly with a proprietary worm remedy against roundworms, and sows should be washed with soap and water and dosed before being put into the farrowing quarters. This destroys any internal worms and eggs that may be on the skin of the sow. All pigs should be given routine dosing against tapeworms. Eggs produced by tapeworms inside the animal hatch in the intestine, pass through the wall into the bloodstream and are carried around the body where they form cysts.
If undercooked, infected meat is eaten by man, the cysts hatch out and become tapeworms inside the human host. This type of infected meat is called measly because of the small, round cysts.
3. DISEASES OF SOWS
Inflammation of the udder caused by bacteria such as staphylococci, streptococci, coliform, etc., does take place in the case of sows although it is far less common than mastitis in dairy cows. Infection usually occurs within 48 hours of farrowing, and signs are some enlargement, congestion, redness and pain in one or more of the teats and glands of the udder. Often the piglets have to be taken off the sow and reared by bottle. Infection can be brought on by injuries to the udder, chills, damp floors, udder tension and high milking capacity. Treatment consists of applying antibiotics up the teat or by drenching the sow orally with sulphonamides.
This occurs within a week of farrowing. The early signs are reduced appetite and some uneasiness, but it will become evident by the collapse of the sow, inability to rise and loss of interest in the piglets. The udder becomes hard, the piglets cannot get milk and if left untreated the sow will die. As in the case of the cow, injecting a solution of calcium borogluconate affects a rapid recovery and the piglets can continue to suckle the sow.
This is a serious fever which begins two or three days after normal farrowing. The sow becomes dull, loses her appetite, the udder becomes hard, the temperature rises to 41 – 42 °C, and untreated cases generally cause death. Treatment by sulpha drugs is effective but must be immediate. It is good practice to take the temperature of sows every evening and morning for 3 days after farrowing, so that any rise in temperature is noticed at once and the sow can be treated. With early treatment the piglets can be left on the mother, but if the sow loses her milk the piglets must be hand fed, at least for a few days.
4. DISEASES OF GROWING AND FATTENING PIGS
This is a nutritional anaemia caused by a lack of iron and it occurs in young pigs from about 3 weeks old. The anaemia is caused by a fall in the levels of haemoglobin, the red colouring matter in the blood which contains iron, and this causes the capacity of the blood to carry oxygen to fall. The skin under the eyelids and the gums of the piglets become a pale pink colour, they may develop diarrhoea, and many of the affected animals
die. Piglets running with a sow on pasture, or with access to soil or turf, seldom develop anaemia. All piglets that are housed all the time should be given an injection of a proprietary preparation of soluble iron at three days old, and they may have to be injected again at three weeks old.
The symptoms of this condition are a high fever and severe diarrhoea in which there are blood clots. It can be caused by a number of factors, the main one being infection by bacteria of the Salmonella group. It is also a symptom in Swine Fever and Swine Erysipelas. It can be caused by eating some irritant material, and temporary enteritis may follow a sudden change in feed. Enteritis caused by Salmonella infection can occur in very young animals but more often it happens in growing pigs and adults. The fever and diarrhoea is often accompanied by pneumonia and mortality is high. Animals that recover frequently become carriers of the disease. Such carriers may bring the disease onto a farm, or it may be introduced through infected feed, particularly feed from animal sources. Treatment is by administering sulpha drugs or antibiotics. Prevention can be helped by isolating animals coming onto the farm and by good hygiene as stress can also be a trigger for the disease.
This occurs in fattening pigs usually between 10 and 16 weeks old and often to the best pigs in the group. The cause is unknown but the disease often follows any abrupt change in feed. The course of the disease is very short, and some pigs may die.
Others go off their feed, develop swollen eyelids and start to stagger, and within 36 hours become paralysed and die. Pigs in a group which show signs of the disease should be given a laxative, starved for 24 hours and fed lightly for a few days. Prevention is mainly by being very careful in making changes in the feed of pigs of all ages. Any change in rations should be done very gradually, over a period of a week.
Outbreaks of respiratory diseases can occur in pigs that are housed intensively, and pneumonia is a common condition. Pigs housed in conditions with good ventilation and plenty of fresh air, are normally free of the disease, but intensively housed pigs, particularly in temperate climates, suffer from a condition called Virus Pneumonia. The symptoms are a cough and the pigs are generally unthrifty although they eat well. The disease also infects suckling pigs and weaners. Prevention is by isolating any new pigs that are brought onto the farm for a month, and any that are coughing should be slaughtered and a post mortem performed. Cases of pneumonia can be treated with one of the sulphonamide drugs or an antibiotic such as Tylan.
DISEASES OF POULTRY
FOWL PEST OR NEWCASTLE DISEASE
This is an acute, highly infectious disease with a mortality rate of up to 100%. It causes a large drop in egg production in laying flocks, and delayed maturity in broiler flocks. The disease spreads rapidly
throughout a flock by birds coughing or sneezing infected droplets, and the virus can be spread by contaminated food, eggs or clothing of workers. The incubation period is 5 days and is followed by dullness, coughing, sneezing and gasping by the birds. All birds in a flock will contract the disease, and mortality is often 50%, and even higher in baby chicks. There is no treatment for the disease and some countries follow a policy of slaughtering all infected birds together with their contacts. Control can be achieved by a combination of good hygiene and immunity by vaccination. Laying flocks must be vaccinated at least twice a year, while broilers can be vaccinated once. The vaccine used can be dead or live, the dead vaccine being easier to handle. Using the dead vaccine, young chicks are vaccinated at 10 – 14 days old and again 2 – 3 months later, and this should be routine in all poultry units.
This disease is caused by bacteria of the Salmonella group and adult birds are most commonly affected. Infection is spread by droppings from infected birds, and those birds that have recovered can act as carriers of the disease. Incubation is 4 – 5 days, after which the birds become depressed, cease feeding and develop bright yellow diarrhoea. Death can occur in 3 – 6 days. Treatment of the disease is to slaughter affected birds and treat the rest with the drug furazolidone at the rate of 0,04% in the mash for 10 days. The flock should be blood tested and any reactors slaughtered and their carcasses burnt as these are carriers of the infection. The flock should then be removed to a clean area of the farm where the survivors can be vaccinated to prevent any further outbreaks.
BACILLARY WHITE DIARRHOEA
BWD is a disease of baby chicks in which infection is transmitted via the hatching egg. It is also caused by bacteria of the Salmonella group. In the acute form, chicks die immediately after hatching, followed by a further 3 – 4 weeks with a mortality rate of 20 – 80%. If infection occurs after hatching they will die between 1 and 3 weeks of age but more birds suffer from the disease, recover and become carriers. The white chalky droppings, that foul the vent feathers and which give the disease its name, do not always occur. The disease can be treated with Furazolidone in the mash, but prevention can be achieved by blood-testing all birds over 5 months old every year in areas where the disease exists. All reactors should be slaughtered. All incubators and other poultry equipment should be treated with a disinfectant as a routine measure
Is a highly infectious and fatal disease caused by Pasturella bacteria. Infection is from a carrier bird brought onto the farm or introduced by wild birds. The disease is spread by infected oral or nasal discharges contaminating food and water in the poultry house, and by contaminated dropping. In acute outbreaks there are no symptoms and birds are found lying dead.
In less acute cases, symptoms vary from depression, drowsiness, coughing, sneezing and diarrhoea which can be green, purple wattles and combs and a liquid discharge from the eyes. Treatment is not economical and affected birds should be slaughtered, burned and all houses disinfected. Prevention is through good management and hygiene, and any birds introduced onto the farm or poultry unit should be kept in isolation for a month. Birds can be vaccinated against the disease at 8
– 12 weeks old. Young birds and growing pullets should never be mixed with older, laying stock.
This is a virus disease which can affect birds of all ages and particularly those between 6 and 12 months. The virus can be transmitted by ticks, lice, mosquitoes and other biting flies, and it is passed on by direct contact between birds.
The virus enters the skin through small cuts and scratches particularly on the head and wattles, and produces small, watery pustules on the head, comb and wattles, and around the corners of the
mouth. After a few days these pustules dry into a brown crust and run together to form large grey or brown wart-like growths. In another form of the disease, small white patches occur at the corners of the beak, on the sides of the tongue, the roof of the mouth and the epiglottis. These patches spread and can cover the tongue and the sides of the mouth and throat. There is no treatment for the disease but it can be prevented by vaccinating the growing birds at 4 – 5 months old, and at least 3 weeks before laying begins.
This disease is caused by a protozoan parasite, a small parasite belonging to the same group of germs that cause malaria in man. The disease is spread by infected dropping which contain oocysts of the organism, and these ripen in conditions of warmth and moisture within 48 hours. Birds eat the infected droppings and develop the disease. There are two types of the disease, the acute and the chronic forms. The acute form,
known as Caecal Coccidiosis usually occurs in young chicks during the first few weeks of life. The chronic form, intestinal Coccidiosis is more common in older birds. The two types are caused by different species of the parasite. Coccidiosis is found in a wide range of animals, but each type of coccidium is specific to a species. For example, the coccidium of the rabbit will not affect poultry.
Outbreaks of coccidiosis vary in severity from those in which only a few chicks are infected to those in which over 50% of the chicks die. In acute outbreaks chicks may be found dead without any signs of illness. Generally, the first symptom seen is the passing of dark-coloured or blood stained droppings. The affected chicks appear to be listless, have a pale appearance about the head and comb and ruffled feathers. The disease can be prevented by not allowing chickens to have access to infected droppings. Battery-rearing cages, houses with wire floors or range units prevent the disease occurring. In deep litter houses, the water and feed troughs should be raised above the floor to prevent the litter from becoming damp. Alternatively, there are a number of drugs available called coccidiostats which can be added to the drinking water. These can be used to prevent the disease, and if at higher levels, to treat infected birds. Good ventilation, good hygiene and thorough disinfecting of housing and equipment are also good preventative measures.
For other diseases of poultry, see Lecture 10 of Poultry Production.