TREATMENT AND CONTROL OF SWINE RESPIRATORY DISEASE

Introduction

Respiratory disease in swine, despite the exponential adoption of All-In/All-Out production within United States and Canada, remains a major constraint to profitability. Today I would like to describe some of the control and treatment methods available in a disease outbreak. To control and treat disease we should understand the pig’s protection mechanisms against respiratory pathogens and how this mechanism is broken down by contributing factors of respiratory disease. Through our discussion, we will understand how environmental and management practices are the most consistent means of control against repiratory disease.

Protective Mechanisms

The pig’s protection mechanism consist of both physical and cellular barriers which prevent entry of infectious agents or destroy the agents that have come in contact with the pig. Nasal airways and the mucociliary apparatus are two physical barriers. The nasal passage provides a physical barrier to particles greater than 5 um in diameter and smaller particles are handled by a mucociliary clearance apparatus. This apparatus is composed of fine hair-like structures which move the particles back up toward the mouth of the pig where the particles are then swallowed. Within the lung there exists a cellular defense mechanism called pulmonary macrophage cells. Macrophage cells act to neutralize pathogens (bacteria or virus). If this is not effective then the macrophage will recruit another cell-type, neutrophils, to remove debris and pathogens. Antibodies and T-cell production are triggered by the presence of pathogens. An immune animal is one which has previous exposure via natural infection or vaccination. A nonimmune animal is one that has no previous exposure to the pathogen. Maternal antibodies or passive immunity is the protection that piglets receive from drinking the sow’s colostrum. While the sow continues to be a major reservoir of pathogens, maternal antibodies transferred to the piglets prevents pathogens from penetrating the piglet’s system. Maternal antibodies tend to breakdown near the time the piglet is developing it’s own antibodies. Therefore there is a period at 3-5 weeks of age when the piglet has low levels of protection.

Transmission of Disease: 2 Primary Mechanisms

1) Pig to Pig: The nose, mouth and trachea is a habitat for many organisms. Organisms which do not promote an immune response are called commensal. Conversely, organisms which release toxins, destroy tissue or lower the immune system are deemed pathogens. Commensal organisms such as Haemophilus parasuis (Hpp) and Streptococcus suis (Strep. suis) can thrive when piglets are exposed while protected by maternal antibodies, without clinical signs of disease. However, nonimmune pigs (SPF or SEW pigs), not previously exposed to Hpp and Strep. suis may result in severe respiratory disease in the presence of primary pathogens.

2) Airborne Transmission: Organisms such as M. hyopneumonia (MH), Porcine Respiratory Coronavirus (PRCV), Swine Influenza Virus (SIV), and Pseudorabies virus (PRV) are capable of airborne transmission up to several kilometers in distance. Airborne spread is facilitated by prevailing wind velocity and direction, cloud cover and humidity.

Predisposing factors for Increased Risk of Respiratory Disease

  • Management systems which do not employ all in all out
  • Large number of pigs with large variation in age in one barn or air space
  • Frequent moving and sorting of pigs through the barn
  • Positive disease status of replacement or supplemental stock
  • Overcrowding and increased pen density
  • Changing weather patterns creating stressful conditions especially in outdoor or nonmechanical ventilation systems. During the winter months there is less air exchange.

Control Strategies

There are two primary goals to disease prevention:

Goal # 1) minimize the “dose” or number of pathogens to pigs by;

  • matching health status
  • reducing number of sources
  • early (between 14 and 21 days) and segregated weaning
  • proper ventilation and contaminant removal
  • maintain acceptable pig density

Goal # 2) to interrupt the natural build-up of pathogens within the pigs environment;

  • good hygiene
  • utilizing All-In/All-Out
  • partial depopulation
  • multi-site production

Treatment and Control of Disease

Management Strategies

  • Ensure adequate air flow from a fresh source, especially in the winter months. pre-warmed but not from a communal air chamber.
  • Reduce fluctuations in temperature and high humidity within the pig space
  • RH at 50 70%
  • Provide proper stocking density.
  • Provide All-In/All-Out from farrowing to finishing. No more than 3 weeks age variation per air space will reduce disease and improve growth performance.
  • Isolate all incoming replacements stock for at least 30 days prior to introduction to the rest of the herd. Introduce larger groups of replacements less frequently and avoid outside replacements if economical.

Actinobacillus pleuropneumonia (App)

Subclinical carriers of App are the primary cause of outbreaks. Serology (30 samples) from pigs at 7-8 weeks of age is important to determine if App carriers are present, isolate App serotype, and determine sensitivity to antibiotics. Positive results from serology taken from 7-8 week old pigs denotes; a recent infection, presence of carriers, and an active infection in the herd.

1) IF your herd is Positive on serology but negative for clinical signs.

Use serology to measure presence of other pathogens which are contributing factors such as PRRS, M. hyo, salmonellosis, and atrophic rhinitis.

2) IF your herd is Positive on serology and positive for clinical signs.

Use serology to measure presence of other pathogens which are contributing factors such as PRRS, M. hyo, salmonellosis, and atrophic rhinitis.

Antibiotics: Injection of pigs as soon as they show clinical signs of anorexia, breathing difficulty and depression (dog sitting). Sick pigs should be injected twice a day for as long as they are sick. Compliance is difficult because this is labor intensive, time consuming and expensive. Mass medication using drinking water medication may be useful. Feed additive antibiotics are of little value against App because pigs are generally not eating and the minimum levels of antibiotic required in the blood to kill the organism is not attainable via feed grade regardless of dosage levels. Besides, feeding pigs at rates above the licensed levels is illegal.

Vaccination:Current vaccines do not reliably prevent pleuropneumonia but MAY reduce mortality rate if the vaccine serotype matches that of the serotype on your farm. Vaccine serotypes do not provide crossprotection against other serotypes. Vaccination of sows may reduce piglet protection by colostral immunity.

Replacement stock must be App negative. Serology on entry and again 30 days later.

Full or partial depopulation: Full: Cost effective when 30% + of unvaccinated sows are App positive.

Eradication: Not an effective method. Many eradication efforts fail. Takes about one year. Must empty the weaner and finishing facility in a farrow to finish operation. Test and cull sows which are positive for App.

Lung lesions resolve in 1-2 months, therefore slaughter checks may not be indicative of App.

3) IF your herd is Negative for clinical signs and negative on serology.

Ensure that breeding stock from supplier is negative and remains negative.

Question if App vaccine is used in gilts prior to entry

Serological Monitoring using ELISA tests for App.

Mycoplasma hyopneumoniae (M. hyo)

Transmission is primarily from pig to pig although long range aerosol transmission is possible. M. Hyo has been isolated from lungs of clinically normal pigs. Based on serology surveys, nearly all commercial swine herds have M. hyo. Clinical signs within the herd (coughing, depression and poor growth rate) are dependent on the dose of infection, contributing pathogens and environmental stress. Many producers are utilizing All-In/All-Out for the farrowing and nursery units. Therefore pigs are not affected until the finishing units when pigs of various ages are exposed to M. hyo carriers.

Antibiotics: Many antibiotics are shown to be effective in a laboratory setting but the effectiveness is questionable in the herd. While antibiotics may improve growth performance during administration, once the antibiotic has been removed, clinical signs and poor growth performance resume.

Vaccination: Commercial vaccines are available and tend to reduce to severity of clinical signs (i.e. coughing) but have not always demonstrated an advantage in growth rate.

Atrophic Rhinitis (AR)

The severe and progressive form is caused by a combination of two bacteria: Bordetella bronchiseptica and Pasteurella multocidaB. bronchiseptica lines the mucosa of the nasal passage allowing the adherence of toxin producing P. multocida which destroys the nasal cavity and turbinates. Some transmission of bacteria is from the sow to the piglet, but transmission after 3 weeks of age is generally from one pig to another via droplets.

Antibiotics: First and foremost, proper testing is required to determine drug sensitivity of the bacteria. Antibiotics such as oxytetracylines and sulfonamides can be used in feed medication in the last month of gestation to control the shedding of bacteria from sows to her subsequent litter. Injectable oxytetracyclines and potentiated sulphonamides (under a veterinary/client relationship) are often used under a program for piglets which consists of three to four injections in the first 21-28 days of life.

Vaccination: The vaccination program is targeted to protect piglets before infection. Vaccinate sows (prefarrow) with a vaccine containing the appropriate P. multocidatoxin. Vaccination of piglets must be performed 2 weeks prior to natural exposure of the bacteria.

Salmonella cholerasuis: S. cholerasuis is a species specific organism transmitted by feces from clinically infected or carrier pigs. Diagnosis is based on clinical signs, necropsy, bacterial culture and histology results.

Antibiotics: Injectable antibiotics provide the most effective treatment in outbreak infections. Affected pigs may continue to eat and drink, therefore mass medications using appropriate antibiotics in the feed and/or drinking water may reduce death loss.

Porcine Respiratory Disease Complex(PRDC)

Porcine Reproductive and Respiratory Virus (PRRS), Swine Influenza Virus, Porcine Respiratory Coronavirus, and Pseudorabies.

Respiratory disease caused by PRRS, in itself, is infrequent in pigs. Concurrent respiratory infections of PRRS and bacteria are common. Pat Halbur at Iowa State University and David Zeman at South Dakota State University have determined that of the swine respiratory disease cases submitted, greater than 50 percent of the PRRS submissions where complicated with bacterial infections such as P. multocidaStrep. suisHaemophilus parasuis and S. cholerasuis.

PRRS, Mycoplasma hyopneumonia, Swine Influenza Virus and Actinobacillus pleuropneumoniae are the most common primary agents involved in the Porcine Respiratory Disease Complex (PRDC). This complex tends to affect pigs at 18-20 weeks of age. Treatment and control of this complex is based on proper diagnosis using a combination of detailed clinical history, serology and necropsy. Long term control strategies include segregated weaning, All-In/All-Out in each stage of growth, ventilation modifications and biosecurity measures.

Take-Home Message

A poorly managed hog farm with a high incidence of respiratory disease was used in a clinical trial to determine whether use of a particular antibiotic would improve growth performance on this farm. The farm facilities were not large enough to replicate the trial, therefore some of the pigs from this farm were moved to the university farm. The original hog farm was continuous flow and of poor conditions in terms of ventilation, high pig density and inadequate sanitation procedures. The university facility had good sanitation and better management practices. As in the children’s rhyme: some piggies stayed home, while others went off to the university. The pigs at the home farm treated with antibiotics improved in growth performance over the untreated pigs at home. The pigs which went off to university, both the treated and the untreated outperformed the treated stay at home pigs. The moral of the story is that management and environment is the better choice over medication for respiratory disease control. OR Be cool and stay in school.

Most common pig diseases

common pig diseases

Pig producers, just like any other animal farmers are well aware of the fact that in order to be successful in their field, they must ensure the health of their pig stock. Given that prevention is the best measure to avoid losing valuable animals, it’s important to know which are some of the most common pig diseases, their symptoms and treatment methods. It should also be noted how important it is to work with specialists – veterinarians and technicians – to establish a herd health plan to cover the three stages of the pig production (pre-weaning, growing-finishing, and breeding).

Pig diseases in the pre-weaning stage

1. Exudative dermatitis (greasy pig disease)

This disease is caused by an infection with the Staphylococcus hyicus bacteria and it manifests through skin lesions. Mortality can occur due to greasy pig disease in severe cases that are left untreated. The lesions first appear as dark spots on the skin, which spread and become flaky, with a greasy feel.

The infection is treated with antibiotics, skin protectants, and autogenous vaccines. One of the best prevention methods is to improve hygiene conditions in the piglet housing areas. It is also recommended to perform teat dipping on the sows as well as pre- and post-farrowing. By reducing the potential of skin abrasions, the infection is prevented from entering the piglet’s system. Skin abrasions can be caused by rough floors, sharp equipment, jagged teeth or mites’ bites.

2. Coccidiosis

Coccidiosis is very common in suckling pigs, being caused by three types of the coccidia intercellular parasite. The main symptom is diarrhea, which can also be bloody and it occurs during between 10 and 21 days of age and up to 15 weeks of age. Acute cases can be treated with coccidiostats and fluid therapy. Because the intestinal wall can be damaged in some cases, secondary infections may occur.

Sows can be treated with coccidiostats in order to prevent this disease. It’s also good to improve hygiene conditions on the farm, to end the circle of infections. Sow feces are a major source of infections. In addition, flies drawn to the feces can further spread the infection. To prevent the occurrence of parasite infections, it is recommended to maintain a warm, clean and dry creep area on the farm.

pig farm housing

Pig diseases in the post-weaning stage

1. Respiratory diseases

The most common symptoms of respiratory diseases are coughing, sneezing, heavy breathing, reduced growth, and even mortality. To treat this type of diseases, antibiotics are often given in feed or water or as injectable substances. Certain environmental conditions or poor ventilation can worsen respiratory diseases or help spread them. For example, high levels of ammonia found in the environment can damage the respiratory tract and thus making pigs more prune to infections.

Among the infectious agents responsible for the occurrence of respiratory diseases are Streptococcus suis and Pasteurella. Some forms of pneumonia can be prevented through vaccines, but it’s important to identify the strain present on a farm to fight against this disease in an efficient way. Especially pleuropneumonia, caused by Actinobacillus pleuropneumoniae can cause a high mortality rate and the surviving pigs suffer from reduced growth rate and lung damage. Along with the presence of respiratory viruses, overcrowded and dirty housing are predisposing factors for respiratory diseases.

2. Swine dysentery

Pigs that suffer from dysentery have diarrhea, with or without the presence of blood. This disease is caused by the bacteria Brachyspira hyodsenteriae. Pigs that suffer from dysentery in the post-weaning stage have reduced growth rate; in more severe cases sudden death can occur.

Swine dysentery is also treated with antibiotics which are given through feed or water, or as injectable substances. To reduce the infection, it’s recommended to reduce the stock density. Improving hygiene and rodent control can also significantly help prevent and reduce the potential of infection. Rodents are important when it comes to the spreading of swine dysentery. The disease can occur when new stock is introduced on the farm, so it’s important to always buy pigs from reliable sources and to request a thorough medical check-up.

Pig diseases in the breeding stage

1. Mastitis

Mastitis is a disease present in sows and it has symptoms such as reduced milk production, higher body temperature and loss of appetite. The disease is caused by a bacterial infection of the mammary glands, where skin discolorations can be observed. Antibiotics and anti-inflammatory drugs are the most efficient treatment for mastitis. Usually, a combination of oxytocin and corticosteroids is prescribed to treat mastitis.

Like in the case of other pig diseases, improving hygiene in farrowing houses is extremely important. Healthy nutrition during the late pregnancy stage is an important factor to increase immunity. Stress is also considered a factor in the occurrence of mastitis, especially if the teats may suffer damages in the sow housing facilities. Mastitis has an important effect on productivity because the number of piglets weaned by sows can be significantly reduced.

2. Porcine parvovirus

Pregnant sows can become infected with the parvovirus (PVV) and in some cases, reproductive diseases can occur. Usually, the reproductive disease occurs in gilts, the reproductive performance being overall affected. Pig litters are decreased in size because of stillbirths and mummification. The parvovirus is somewhat more difficult to diagnose because other reproductive diseases present similar symptoms. The virus can survive outside its host for several months.

PPV is problematic usually during pregnancies, but other pigs can also spread the disease. As there are no treatments for this disease, prevention is extremely important, through regular vaccination of gilts.

pig farm housing

Other common pig diseases and health problems

1. Malnutrition

This is one of the most common pig diseases, easily recognizable because the animals grow slowly and are visibly thin. In healthy pigs, the only bones that should be visible are the shoulder blades. If farmers can notice the backbone, the hips or the ribs, the pigs are too thin. Pigs have a great advantage of growing rapidly. If they are growing too slowly, it’s most likely because of malnutrition.

Malnutrition occurs because of insufficient or poor quality feed. Growing pigs need more feed and of higher quality than adults. Lactating sows also need more high-quality feed to produce milk; otherwise, they will start to lose weight.

2. Lice and flies

As major factors in the spreading of diseases on pig farms, lice and flies infestations pose a serious health threat. Pig lice are rather large and very easy to spot. They can cause blood loss and the infection with bacteria. Flies can also be a problem because they enter open wounds and cause infections. Both lice and flies can be treated with sprays. Ensuring proper hygiene in the housing areas, using fly traps and flypaper can prevent infestations.

3. Parasites

Roundworms are the most common parasites found in pigs. They live in the gut, have a worm-like appearance (hence the name) and cause weight loss. Young pigs present the highest risk of infestation. Roundworms can block the gut and cause death. Even if the pigs survive, if the parasites are not eliminated, the pigs’ growth is permanently reduced. The parasites are eliminated with dewormers which are injected, dosed in the feed or drenched.

Tapeworm parasites live in the muscle of the pigs and cause pig measles. The pigs are seemingly not affected, but they can experience pain and have difficulties to move around. Pig meat infected with tapeworms is very dangerous for human consumption. Undercooked infected meat contains tapeworm cysts, which develop into worms in the intestines and cause serious health problems. Infected pigs can’t be treated for this parasite, but farmers should take preventive measures such as practicing good hygiene and stopping pigs from wandering around outside from the farm.

4. Salt poisoning

Salt poisoning occurs because of improper feed. Pigs fed with restaurant leftovers or with food leftovers from various sources may contain too much salt. Pigs affected by salt poisoning appear to be blind, they lose their balance and fall over, they vomit and have seizures. To prevent this problem, farmers should always ensure quality feed for their pigs.

5. African swine fever (ASF)

Outbreaks occurred over the last years makes this disease more common than it used to be. African swine fever is caused by the Asfarviridae family of viruses, which are distinct from the viruses associated with Classical swine fever. There are 22 known types of the ASF virus. The ASF infection can be introduced through several ways: contaminated feed, tick, and lice bites, contaminated medical equipment and infected pigs.

There is no treatment for the African swine fever or a live or attenuated vaccine to prevent this disease, therefore strict biosecurity measures are the only ways to prevent infection and the spreading of infections. Infected animals must be isolated and culled immediately if the presence of the virus is confirmed.

6. Foot-and-Mouth-Disease (FMD)

FMD is caused by a picornaviridae aphthovirus. There are 7 main serotypes which have in their turn many strains. More than 60 subtypes of the virus have been identified so far, therefore it’s difficult to develop an effective vaccine against it. The symptoms of FMD include lameness, excessive salivation, blisters, loss of appetite, fever, and death in severe cases.

Routine vaccination is used mainly to protect the breeding stock from FMD. However, vaccination is problematic because its protection is only short-lived. Since FMD usually occurs during winter, pigs should be vaccinated in the autumn. Furthermore, because there are several serotypes, the vaccines must be multivalent in order to be effective. The disease can be spread to and by other farm animals as well, so preventive measures should be enforced to cattle, sheep, and goats as well. There is no treatment for this disease and infected animals should be culled.

7. Rabies

Rabies is an infectious disease found in all species of homoeothermic animals, transmissible in humans, characterized by severe nerve disorders, expressed by hyperexcitability and aggression, followed by paralysis and death. To a greater or lesser extent, all warm-blooded animals are susceptible to rabies infection. In pigs, rabies usually evolves in a quick form and is manifested by strong hyperesthesia. Incubation is between 15-30 days. The pig becomes aggressive, shaky, shrieks or shouts in a hoarse voice, quickly attacks other pigs or other animals, causing serious wounds by pulling tissues. The sows devour their piglets.

To prevent rabies, farmers should be aware of the application of a complex of general sanitary-veterinary and immunoprophylaxis measures. Unfortunately, animals infected with rabies can’t be saved and the final outcome is death.

pig diseases prevention

Disease prevention in pigs

Since prevention is the most efficient way to avoid pig diseases and other health problems, it’s important to know which are the main measures to take for disease prevention in pig farms. While some disease or health problems are treatable, others can’t be treated and can become highly damaging for the entire pig stock. Some of the most important measures for diseases prevention include the following:

  • Pigs must be grown in enclosed spaces respecting hygiene conditions, the microclimate and their well-being, isolated from landfills or areas populated with other swine or wild boars;
  • Farmers must work closely with veterinarians to prevent diseases, infections and other health problems which occur in pig farms;
  • New stocks should be purchased only from sanitary-approved holdings, accompanied by official documents;
  • Feed and water must be ensured with respect to quality parameters and without administering in the feed of pigs slaughterhouse waste or non-sterilized household or restaurant waste;
  • Compliance with the welfare rules and the hygiene conditions in the means of transport for the moving swine;
  • The veterinarian should be notified immediately of any signs of disease or mortality in animals;
  • Farmers should collaborate with the veterinarian appointed for the clinical examinations and the collection of samples for laboratory examinations;
  • Fresh meat and pork products resulting from pig slaughtering in their own facilities should be consumed and/or sold only after the specialized examination provided by the veterinarian or local authorities;
  • The bodies of dead pigs infected or suspected to be infected with contagious diseases must be handled by neutralization units, with the support of local authorities.