Pneumonic Pasteurellosis

10/03/2025

Pathogenesis of the disease

Pasteurella haemolityca, P. multocida and Hamophilus somnus are normally found in the nasal pharyngeal mucosa but not in the lungs. In stress due to transport or viral infections such as IBR and PI3, P. haemolityca multiplies rapidly and its toxins cause severe fibrinopurulent bronchopneumonia. When it reaches the lungs, the fight between the bacteria and the host results in tissue destruction.

Etiology and epidemiology

The morbidity rate of the disease is generally 35%, varying between 15% and 45%. The highest morbidity rate is between 16-21 days after being put into fattening. The lethality rate in diseased animals is between 5% and 10%. Mannheimia haemolityca, the main causative agent of the disease, is divided into two biotypes, A and T, according to its biochemical and cultural characteristics. Carbohydrate fermentation, colony morphology, penicillin sensitivity, sensitivity to dyes such as methylene blue, brilliant green, basic fuchsin, and lectin agglutination are used in biotyping processes. Pasteurella haemolityca has 13 serotypes (A1, A2, A5, A6, A7, A8, A9, A11, A12, A13, A14, A16, A17) belonging to biotype A and 4 serotypes (T3, T4, T10, T152) belonging to biotype T. The main agent of the disease is Mannheimia heamolytica A1. The most commonly isolated serotypes are 6, 2, 9, and 11. Pasteurella multocida A3 also plays a lesser role in the disease. In addition, Hemophilus somnus is increasingly encountered. In addition, viruses such as Bovine Herpes Virus, Bovine Viral Diarrhea Virus, Parainfluenza Virus type 3 and Bovine Respiratory Syncytial Virus have been detected in cattle, Retroviruses in sheep and goats, and Caprine Arthritis Encephalitis Virus in adult goats. Mycoplasmas have been detected together with other pathogens in 50-90% of cases. Chlamydial agents are rarely isolated. They increase the pathogenicity of other infectious agents.

Relationship with the immune system

It is known that many infectious agents, weakening of the host defense system and environmental conditions play a role in the development of the disease in ruminants. The reason why the disease is called transport fever in particular is that it occurs frequently in animals that are transported. Pasteurellosis can constitute 40-50% of the diseases seen in a year in beef cattle.

It is seen in 6-24 month old beef cattle, especially shortly after fattening, 6-8 month old and weaned beef calves, and less frequently in young calves and adults. The disease, which occurs especially in the fall, can occur in adult beef cows when they are moved in large groups during the summer months or rainy seasons, during harsh stormy weather. Passive antibody transfer is an important factor in protecting calves younger than two months from the disease. However, if other risk factors occur very severely, the risk of developing the disease is high even if the level of passively received immunoglobulin is high. Inadequate intake of energy, protein, vitamins and minerals required for immune response creates a predisposition to pneumonia in animals. In addition, copper, selenium, zinc, manganese, iron, vitamins A and E deficiencies play important roles in reducing resistance to diseases.

The importance of clean air

When the daily amount of milk given to calves is reduced due to fear of neonatal diarrhea in dairy farming, an energy-protein deficit occurs. The high presence of pathogenic agents, dust and gases such as ammonia in the air of calves raised in closed barns, irregular ventilation in the barn and breathing dirty air together with clean air increases the risk of pneumonia. Keeping calves raised for meat in crowded barns, collecting calves from different places and the difference in the amount and quality of colostrum they receive increases the incidence of pneumonia. The risk of pneumonia is high in calves with neonatal diarrhea.

Condition of the shelters

The shelters on the farm where the food will be produced should not be too crowded and animals coming from different shelters should be kept as separate as possible. Nutrition and environmental conditions should be good. Operative interventions should be carried out immediately after transport. In shelters where many animals brought from different regions are kept together, infectious agents spread very quickly and cause deaths in the herd.

Symptoms of the disease

In the initial period of the disease, there are signs of mild depression and loss of appetite, and an increase in body temperature. Patients are determined to have serous or mucopurulent lacrimation and nasal discharge, increased respiratory frequency and cough. Lung sounds are detected to become more pronounced during auscultation. The severity of clinical findings increases in those infected with secondary bacteria.

In cases where bronchopneumonia develops, respiratory system inflammation and toxemia occur. The fever is over 40°C. Patients stand apart from healthy people, have signs of depression, do not approach food, and keep their heads and ears down. Ocular and nasal discharge become mucopurulent. The sound obtained during auscultation of the lungs is louder than at the beginning, and especially in chronic cases, crackles followed by wheezing can be heard within a few days. A dull sound is detected in the right ventral area, especially in percussion of the lungs.

Diagnosis

Diagnosis is made in light of clinical findings and the agent is isolated. Laboratory findings mostly include leukocytosis, leukopenia in severe cases, mild neutrophilia and shift to the left in bacterial infections. Immunofluorescence, immunoperoxidase staining and antigen capture enzyme immunoassay tests are used in viral cases. Detection of viral nucleic acids is another diagnostic method. Antibodies in blood serum can be detected by serological tests. In herds, animals are observed from a distance and the affected ones are seen to be depressed and shallow but rapid breathing. The cough intensity increases when the animals are walked.

What should be done to minimize the risks?

Risk factors related to the host and the environment regarding pneumonia in calves reared for meat;

• Farm where calves are located

• Transportation of animals

• Risks in the fattening area

To minimize these risk factors; the surgical procedures of the calves should be completed at least 3 weeks before transportation, the calves should be weaned, they should be accustomed to mass feeding conditions, they should be vaccinated against respiratory infections and calves should be given nutrients in order to support their immune system.