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Porcine pasteurellosis is one of those diseases that can put an end to all the farmer’s plans for making a profit from pig farming. The most susceptible to this infection are piglets, which are usually raised specifically for sale. Adult pigs also get sick, but less often and tolerate the disease more easily than piglets.
What kind of disease is pasteurellosis?
This bacterial disease is thought to be common to many animal species, including humans. The latter is usually infected with pasteurella from domestic animals. The causative agent of the disease in pigs is the non-motile bacteria Pasteurella multocida types A and D and Pasteurella haemolytica. Signs of pasteurellosis vary widely depending on the species of animal from which the bacteria culture was obtained.
Pasteurella are classified into 4 serogroups: A, B, D, E. All these groups are similar in appearance and antigenic properties. Pasteurellas look like motionless oval rods 1.5-0.25 microns long. They belong to gram-negative bacteria. There is no dispute.All varieties of pasteurella grow on the same nutrient media, preferring the presence of blood in the broth.
Pasteurellas are not highly resistant:
- when dried, they die after a week;
- can live in manure, cold water and blood for up to 3 weeks;
- in corpses – 4 months;
- in frozen meat they remain viable for up to a year;
- when heated to 80 °C they die in 10 minutes.
Bacteria are not resistant to disinfectants.
How dangerous is the disease?
Pasteurellosis usually develops along the path of epizootic. Soon after one individual is infected, the entire pig population on the farm becomes ill. Most often, acute and hyperacute pasteurellosis is observed in piglets. In adult pigs, a chronic course occurs. Due to the nature of chronic pasteurellosis, animals are often treated for other diseases, contributing to the spread of pasteurellosis.
Causes and routes of infection
The bacteria are excreted along with the physiological fluids of the sick animal. Apparently healthy but recovered pigs can be carriers of the bacteria. Infection occurs through direct contact of animals through airborne droplets. Also, a healthy pig can become ill with pasteurellosis through water and feed contaminated with feces or saliva. Pasteurellosis can be carried by blood-sucking insects.
The preservation of bacteria in the external environment is facilitated by:
- untimely cleaning of machines, which increases humidity as a result of urine evaporation;
- low-quality feed, which reduces the immunity of pigs;
- high crowding of animals, due to which pigs experience stress, which also leads to suppression of the immune system;
- lack of vitamins in the diet.
Outbreaks of pasteurellosis were also noted after vaccination against plague and erysipelas.
Symptoms of the disease in different forms
Pasteurellosis is a “variable” disease. Its symptoms vary not only depending on the type of disease. There are 4 types of disease:
- hyperacute;
- spicy;
- subacute;
- chronic.
They differ in the length of time that passes from the moment the first symptoms appear until the death of the pig. How pasteurellosis will progress in each individual pig depends on the virulence of the bacteria and the resistance of the animal’s immune system to the pathogen.
Ultra-acute form
In the hyperacute form of pasteurellosis, the death of pigs occurs after a few hours. Signs of the hyperacute form:
- temperature 41-42 °C;
- thirst;
- refusal of food;
- depressed state;
- disturbances in the functioning of the cardiovascular and respiratory systems;
- Possible diarrhea mixed with blood and mucus.
The progression of the disease occurs very quickly. Before death, the pig exhibits symptoms of heart failure and swelling of the head. During pathological studies, pulmonary edema is detected.
Acute form
The symptoms of the acute form are the same as those of the hyperacute form. Before death and during research, the same signs are found. Unlike hyperacute, with this course of pasteurellosis, death occurs after a few days.
Subacute form
The subacute and chronic course of pasteurellosis are also similar. In both cases, the disease is characterized by fever and localization of the process in individual systems of the pig’s body. Depending on the location of the bacteria, pasteurellosis is divided into 3 forms:
Intestinal:
- debilitating diarrhea with dark brown or reddish stools;
- blood in manure;
- thirst;
- refusal of food;
- exhaustion;
Chest:
- serous, later mucopurulent discharge from the nose;
- possible blood in nasal discharge;
- labored breathing;
- cough;
Edema:
- inflamed swelling of the eyelids;
- swelling of the tongue and larynx;
- swelling of the subcutaneous tissue in the neck, abdomen and legs;
- difficulty swallowing;
- hard breath;
- secretion of thick saliva;
- heart failure.
Because the symptoms of pasteurellosis vary widely, it is easy to confuse the disease with other infections.
Chronic form
The symptoms and localization of bacteria in the chronic course are similar to the subacute one. But since death occurs after a few weeks, more pathological changes have time to accumulate:
- wasting of corpses;
- fibrinous-hemorrhagic inflammation of the intestine;
- fibrinous-purulent inflammation with necrosis in the lungs.
Since in the subacute and chronic course of pasteurellosis, symptoms in pigs depend on the localization of bacteria, treatment is prescribed only after differentiating it from plague, erysipelas and salmonellosis.
How is the disease diagnosed?
If pasteurellosis is suspected, parts of the corpses of dead pigs are submitted to the laboratory for research. The entire carcass is not needed in the laboratory, since pasteurellosis affects the internal organs. At autopsy, lesions are found:
- Gastrointestinal tract;
- lungs;
- heart muscle;
- spleen;
- liver.
The photo shows the lung of a pig that died from pasteurellosis.
In addition to the lungs and spleen, you can also send to the laboratory for research:
- brain;
- glands;
- lymph nodes;
- tubular bones.
When the biomaterial arrives at the laboratory, Pasteurella is also isolated and a bioassay is performed on mice.
Small pieces of organs measuring 5x5 cm are submitted for analysis. Material only from those animals that did not have time to receive antibiotics during their lifetime is suitable for research.
Treatment of pasteuriliosis in pigs
Sick pigs are separated and placed in a warm, dry room. Provide complete feeding with high-quality feed. Treatment is carried out comprehensively, using antibacterial drugs and means for symptomatic treatment. Preferred antibiotics are those belonging to the penicillin and tetracycline groups. The antibiotic is used according to the instructions for the drug. Some long-acting medications can be used once, but this must be indicated in the instructions. Sulfonamides are also used.
To enhance immunity, serum against pig pasteurellosis is used. It is administered once intramuscularly or intravenously at a dose of 40 ml per animal.
On sale you can find whey produced in Belarus and Armavir. It follows from the instructions that the difference between these two drugs is in the timing of the formation of passive immunity and the timing of protection against pasteurellosis.
After using Armavir-made serum, immunity is formed within 12-24 hours and lasts for 2 weeks. In Belarus, immunity is formed immediately after use, but lasts only 1 week.
If there are sick animals on the farm, serum against pasteurellosis of pigs is also used as a prophylactic agent for animals that appear healthy. Clinically healthy piglets under a sick sow are injected with serum in a therapeutic dose.
If pasteurellosis is detected on a farm, the farm is quarantined. The import and export of pigs outside the farm is prohibited. The carcasses of forcedly slaughtered pigs are sent to a meat processing plant for processing.
Prevention
Prevention of pasteurellosis is, first of all, compliance with veterinary rules. Newly acquired pigs are quarantined for 30 days. The livestock comes from pasteurellosis-free farms. Contacts between pigs from different farms are not allowed.
Do not graze pigs on waterlogged pastures, where pasteurellosis pathogens can persist for six months. Regular deratization of premises is carried out. Food is stored in sealed containers inaccessible to rodents.
In areas unfavorable for pasteurellosis, mandatory vaccination of pigs is carried out twice a year. On farms where pasteurellosis has been reported, new pigs must either be vaccinated at the supplier during the year or be vaccinated during quarantine. The introduction of unvaccinated animals into the herd is allowed no earlier than a year after the farm has been restored to health.
Vaccine against pasteurellosis
Serum is made from the blood of recovered or vaccinated animals. It contains antibodies to pasteurellosis and is effective immediately after administration.
The vaccine is a preparation containing Pasteurella bacteria neutralized by formaldehyde. The vaccine cannot be used on a farm where pasteurellosis has already been detected. In this case, vaccination may provoke the development of the disease.
On a farm located in a disadvantaged area or that has previously experienced an outbreak of pasteurellosis, vaccination of pigs is mandatory.Only clinically healthy animals are vaccinated.
Vaccination is carried out twice. The formation of immunity occurs 20-25 days after the last vaccination. Immunity lasts for 6 months.
Vaccinated sows pass on immunity to their piglets. The effect of such “milk” immunity lasts 1 month, therefore, from 20-25 days of life, piglets are vaccinated twice with an interval of 20-40 days. Injections are given intramuscularly in the neck. Dose for a piglet 0.5 ml.
Pregnant queens are given a single vaccination with a double dose (1 ml) 1-1.5 months before farrowing. The vaccine is administered intramuscularly into the upper third of the neck.
Conclusion
Porcine pasteurellosis is a disease that can be avoided if the conditions of keeping the animals and their feeding rations are observed. Timely vaccination will significantly reduce the likelihood of pasteurellosis, since the causative agents of this infection are the same in all animals. You can't count on a pig not getting infected from a chicken or rabbit.
