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Bovine pasteurellosis
Bovine pasteurellosis is a bacterial infection of the lungs, the main cause of mortality in young fattening cattle. It is often called “transport fever” because it typically breaks out in the days following a movement or gathering of animal...
What is it?
Bovine pasteurellosis is a bacterial infection of the lungs, the main cause of mortality in young fattening cattle. It is often called “transport fever” because it typically breaks out in the days following a movement or gathering of animals.
The responsible bacteria already live, in small numbers, in the noses and throats of perfectly healthy cattle. They only become dangerous when the animal's defenses drop: stress of transport, mixing of animals, cold or heat, poor ventilation, or prior viral infection.
There is also a devastating form, hemorrhagic septicemia, which affects cattle and buffalo: the bacteria invades the entire body and the animal dies within a few hours to a few days, often with marked swelling of the throat. This form is particularly feared in hot regions.
Key point
Hemorrhagic septicemia is among the diseases listed by the World Organization for Animal Health and is mandatory for reporting in many countries, including Tunisia: any suspected case, and in particular any rapid mortality with swelling of the throat, must be reported to the veterinary services.
Commonly observed signs
These signs are neither exhaustive nor specific. Only a veterinarian can establish a diagnosis.
Related signs — each one links to its page:
Respiratory form: high fever that appears before everything else, often before the breeder even notices anything.
Despondency, animal which remains behind the crowd, head lowered, ears drooping, which no longer comes to the trough.
Rapid, difficult breathing, sometimes strained neck and open mouth in severe cases.
Dry cough, runny nose first clear then thick, watery eyes.
Net drop in milk production in lactating cows.
Grinding of teeth and moaning in animals in pain.
Septicemic form: very high fever, salivation, hot and painful swelling of the throat, from the throat towards the chest, difficulty breathing, animal which lies down and never gets up, rapid death.
In both forms, it is not uncommon to find a dead animal without having been seen sick, especially when fattening.
When to consult without delay
This list does not replace veterinary advice. It gathers situations that justify a prompt consultation.
Causes and risk factors
The bacteria most often involved are Mannheimia haemolytica, Pasteurella multocida and Histophilus somni.
They are normally present in small quantities in the upper respiratory tract of healthy cattle: they are not germs coming from the outside, but germs which take advantage of a weakness.
Stress or a prior viral infection — infectious bovine rhinotracheitis, bovine viral diarrhea, respiratory syncytial virus — damages the mucosa and lowers local defenses. The bacteria then multiply massively and descend into the lungs.
Certain strains of Pasteurella multocida cause the septicemic form, which invades the blood and no longer just the lungs.
Long transport, fasting, in high density, in hot or cold weather.
Mixture of animals of different origins in the same batch: this is the most constant risk factor.
Weaning, sudden change of diet, dehorning or castration carried out at the same time as other manipulations.
Poorly ventilated building, loaded with ammonia and dust, or on the contrary exposed to drafts.
Marked temperature differences between day and night.
Respiratory viral infection in progress in the batch.
Young animals, poorly protected by colostrum or not vaccinated.
Transmission
By droplets projected during coughing and by secretions from the nose, between nearby animals.
By direct nose-to-snout contact, at the trough and at the drinker.
Healthy carrier animals constitute the reservoir: the disease does not always require the arrival of a sick animal to appear.
Contaminated equipment, feeders and drinkers contribute to the spread in a batch.
In the septicemic form, soils and contaminated water points also play a role, particularly in the humid and hot season.
Diagnosis and care
Diagnosis is the veterinarian's responsibility, based on clinical examination and laboratory tests. Care is decided case by case.
The veterinarian takes the temperature, listens to both lungs, assesses the respiratory effort and examines the entire group, because other animals are often affected without being spotted yet.
The rectal temperature taken early in the morning is the best screening tool available to the breeder: a feverish animal should be treated before it runs out of breath.
Respiratory tract samples can be taken to identify the bacteria and test its sensitivity to antibiotics: this is particularly useful when several animals respond poorly to treatment.
The search for an associated virus is often relevant, because it changes the herd's prevention strategy.
In the event of mortality, an examination of the dead animal by the veterinarian guides the treatment of the remaining animals. Warning: in the event of sudden death, you should never open a corpse yourself, other serious illnesses must first be ruled out.
Treatment
It is an emergency: the prognosis directly depends on the time between the first signs and treatment.
Treatment is based on antibiotic therapy prescribed by the veterinarian, chosen according to the bacteria in question and, when possible, according to an antibiogram. Neither the product, nor the dose, nor the duration can be improvised.
An anti-inflammatory is often combined to reduce fever, limit lung damage and restore appetite.
The animal is isolated in a quiet area, in a well-ventilated room without drafts, with clean water and palatable food within reach.
Complete the prescribed treatment to the end, even if the animal seems to be better after two days: premature cessation is the leading cause of relapse and resistance to antibiotics.
Monitor the other animals in the group twice a day: contagion is rapid.
Treatment depends on the cause and the animal's condition: it must be determined by a veterinarian. No self-medication.
Prevention
Limit stress during key stages: do not combine weaning, transport, change of diet, dehorning and vaccination in the same week.
Prepare animals before transport: watering, food transition, calm loading.
Respect stable batches: avoid adding new animals to an already established batch.
Take care of the atmosphere in buildings: effective ventilation without drafts on animals, clean and dry litter, reasonable density, air not loaded with ammonia.
Ensuring a good intake of colostrum in the first hours of life: this is the basis of the calf's resistance.
Control respiratory viruses in the herd, because they open the way to pasteurella.
Take the temperature of animals at risk during sensitive periods, to intervene before shortness of breath.
Vaccination
Vaccines exist against the responsible bacteria, alone or associated with the main respiratory viruses of cattle.
Specific vaccines against hemorrhagic septicemia are used in regions where this form occurs, particularly before the rainy season.
Vaccination must be carried out sufficiently in advance of the risk period – allocation, transport, housing – so that protection is installed on the day the animal needs it. Vaccinating on the day of departure is of no use.
The choice of valences and the calendar depend on the germs present in the breeding and the management of the herd: they are established by the veterinarian.
Possible complications
Irreversible lung damage in animals treated late: the animal survives but coughs, grows poorly and remains fragile.
Pleurisy and lung abscesses.
Involvement of the joints and sometimes the heart or nervous system with Histophilus somni.
Mortality, particularly in the septicemic form and in young animals.
Relapses when treatment was stopped too early.
When to see a veterinarian
An animal is breathing quickly, with difficulty, neck strained or mouth open: call the veterinarian immediately.
An animal has a fever, stays behind the crowd and no longer eats.
Many animals cough in the days following transport or allocation.
A warm swelling appears under the throat or in the chest area: it is an emergency.
An animal is found dead without prior signs: notify the veterinarian and do not open the corpse.
A treated animal does not get better after two days: the treatment must be re-evaluated, not prolonged at random.
Prognosis
Treated within the first few hours, an animal most often heals well and resumes normal growth.
Treated late, it can survive with permanently damaged lungs: slowed growth, persistent cough, relapses with each stress.
The septicemic form is very serious: the progression is rapid and mortality is high despite treatment.
At the batch level, the quality of daily monitoring has more influence on the results than the choice of drug.
Frequently asked questions
Why do my pets get sick right after transport?
Transport combines fasting, fatigue, promiscuity and mixing of animals. This stress lowers the defenses and lets the bacteria already present in the nose invade the lungs. This is why we talk about transport fever.
Can I self-treat with an antibiotic that worked last year?
No. The germ in question and its sensitivity change from one episode to another, and a poorly chosen or poorly used product wastes the hours that matter most. The treatment is prescribed, it cannot be copied.
How to spot a sick animal before it runs out of steam?
By observing the lot in peace twice a day: the animal which stays behind, which does not come to the trough, whose ears fall off. Taking the temperature confirms: fever precedes respiratory signs.
Is the disease transmissible to humans?
These bacteria do not cause respiratory disease in humans under livestock conditions. The usual rules of hygiene remain of course, in particular washing hands after handling animals.
References
WOAH — Organisation mondiale de la santé animale (ex-OIE)
FAO — Organisation des Nations unies pour l'alimentation et l'agriculture
Content reviewed by the TunisieVet editorial team · Updated 09 August 2026
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