Avian Cholera, What You Didn’t Know About This Disease

Fowl Cholera is a bacterium, called Pasteurella multocida. Fowl cholera is a contagious bacterial disease of domestic and wild species of birds caused by infection with Pasteurella multocida. It usually appears in a fulminant, superabundant form with massive bacteremia and high morbidity and mortality rates. One infection can result in high mortality. The disease is transmitted by contact between sick and healthy birds. The epidemic occurs between 4 and 9 days after contracting the disease.

What is Fowl Cholera?

Pasteurellosis is an infectious disease, due to Pasteurella multocida, which affects many people, species of birds. It owes its name to Louis Pasteur, who specified the characteristics of the germ in that it had been discovered as early as 1879 by Toussaint. We face the disease worldwide, sporadic or enzootic, acute or chronic.

Fowl cholera (fowl pasteurellosis) is a common avian disease that can affect all types of birds and has a global distribution. Outbreaks of fowl cholera are often manifested by acute fatal sepsis. Diagnosis depends on isolation and identification of the responsible bacterium, Pasteurella multocida.

Suspected diagnosis may be based on the appearance of characteristic symptoms and lesions or on microscopic observation of very numerous bacteria in a blood or tissue layer, such as the liver or spleen. Attenuated or chronic forms of the disease may also be observed when it is enzootic with localized infections mainly in the respiratory and skeletal systems.

Pathogenic Agent

Pasteurella multocida is easily isolated, often in pure culture from visceral organs such as the lung, liver and spleen, bone marrow, gonads or heart blood of birds that have died of an acute disease with bacteremia or characteristic caseous exudate seen in chronic fowl cholera lesions. This is a facultative anaerobic bacterium that grows best at 37 C.

Primary isolation is achieved using media such as starch dextrose agar, blood agar and tryptic soy agar. Isolation can be improved by the addition of 5% inactivated heated serum. The diameter of the colonies is 1 to 3 mm after 18 to 24 hd incubation and they are discrete, circular, convex and translucent. Cells are coccobacillary or short rod-shaped, 0.2-0.4-0.6-2.5 m in size, Gram-negative, and usually occur singly or in pairs. Bipolar staining is evident with Wright’s or Giemsa stains.

Identification of P. multocida is based on the results of biochemical tests, including carbohydrate fermentation, enzyme production, and production of certain metabolites. Serological characterization of P. multocida strains includes capsular serogroups and somatic serotype. DNA genetic fingerprinting can differentiate P. multocida with the same capsular serogroup and somatic serotype. These characterizations require a specialized laboratory with appropriate reagents for this diagnosis.

Pasteurella avian cholera pasteurella multocida is a Gram-negative, nonmotile, coated, extracellular bacterium. The antigenic structure of the bacterium is complex. It is composed of a capsular antigen = K antigen, which masks the wall antigen or somatic antigen = O antigen. The bacterium is very sensitive to UV rays, desiccation, common disinfectants, and is only resistant for a few days in an outdoor environment.

The classification is complex. Carter’s classification distinguishes 4 types of K antigens: A, B, C and D (A being the most frequent in poultry). The O antigen classifies the pastures into different serotypes, which vary according to the classification.According to Namioka’s classification, the O antigen has 12 serotypes (1 to 12), so pasteurelle is classified according to the combination of capsular and somatic serotypes.

Serological Tests

Serological tests for avian cholera are rarely used for the diagnosis of fowl cholera. The ease with which a definitive diagnosis is obtained with isolation and identification of the organism precludes the need for serological diagnosis. Requirements for vaccines and diagnostic materials: Vaccines against P. multocida generally use inactivated bacteria, with aluminum hydroxide or oil as the adjuvant, prepared from multiple serotypes. Two doses of inactivated vaccine are generally recommended.

Vaccines obtained from live cultures tend to convey superior protective immunity, but are less commonly used because of possible post-vaccination sequelae, such as pneumonia or arthritis. Multivalent vaccines usually include somatic serotypes 1, 3, and 4 because these are the most frequently isolated avian serotypes. Safety and efficacy testing of inactivated vaccines generally uses the host animal.

The activity of the final live culture harvest is tested by counting bacteria from the OIE Terrestrial Manual 2005 Multivalent vaccines usually include somatic serotypes 1, 3 and 4 because these are the most frequently isolated avian serotypes. Safety and efficacy testing of inactivated vaccines generally uses the host animal. The activity of the final live culture harvest is tested by counting bacteria from the OIE Terrestrial Manual 2005 Multivalent vaccines usually include somatic serotypes 1, 3 and 4 because they are the most frequently isolated avian serotypes. Safety and efficacy testing of inactivated vaccines generally uses the host animal. (See Article: Reproduction of chickens)

Epidemiological Data

Many species of birds are susceptible to P. multocida fowl cholera. The disease is most common in turkey, duck, goose and chicken. Man can be accidentally contaminated by a skin lesion. It is an affection of adult or young adult birds, but the disease can appear from 4 weeks of age. Breeders are most frequently affected. There are many healthy carriers among wild birds.

Many factors favor the appearance and development of infection in a farm. Environmental factors are predominant, especially cold. Pasteurellosis is more frequent in autumn and winter. The bacterium persists for a long time and easily in cool, wet soils. Stress factors, such as thawing, thawing, vaccinations, force-feeding, are also highly favored.

Transmission is horizontal, indirect but mostly direct. There does not appear to be any vertical transmission. Reservoirs of P. multocida may be infected farm birds (chronic carriers or (to survivors), or wild birds entering the farm, rats, birds and other animals are also suspected. pigs and domestic mammals. Virulent materials are oral, nasal, conjunctival secretions. All droppings and dirt from sick birds are contaminants.

The bacterium multiplies easily in carcasses. The route of penetration is mainly respiratory, but oral, conjunctival and dermal routes are possible. NB: Caution should be exercised regarding the temporal relationship between contamination (in the microbiological sense) and the occurrence of clinical pasteurellosis. The disease often expresses itself after a period of asymptomatic carriage due to a triggering factor.(See Article: Turkey)

Transmission

Contamination of feed and drinking water is caused by diarrhea or nasal discharge of infected birds under stress (overcrowding, exposure to cold or heat, lack of hygiene, etc.). These conditions lead to a weakening of the birds’ resistance to Avian Cholera infection.

The pulmonary and musculoskeletal systems are often the site of these infections. The most common synonyms for fowl cholera are fowl pasteurellosis and fowl hemorrhagic septicemia. Fowl cholera is not considered a potential zoonosis because the avian strains are generally not pathogenic to mammals exposed orally or subcutaneously.

Other bacterial D diseases, including salmonellosis, colibacillosis, and hen listeriosis and pseudotuberculosis, erysipelas, and turkey chlamydiosis may have symptoms and lesions similar to fowl cholera. Differentiation is by isolation and identification of P. multocida, which is easy to culture in cases of fowl cholera. (See Article: Domestic Duck)

Affected Species

  • Chickens
  • turkeys
  • ducks
  • geese
  • pheasants
  • pigeons and other wild and domestic poultry.

Symptoms

The following symptoms of Avian Cholera can also be observed: hyperthermia, anorexia, apathy, mucous secretion from the mouth, diarrhea, ruffled feathers, drop in egg laying rate with production of smaller eggs, increased respiratory rate and cyanosis at the time of death. Lesions are often observed: congested organs with serosal hemorrhages, hepatomegaly and splenomegaly, multiple small foci of liver and spleen necrosis, pneumonia, mild ascites and pericardial edema.

Birds that survive this acute septicemic form or become infected with less virulent organisms may develop chronic fowl cholera characterized by localized infections. These infections are most often the joints, footpads, tendon sheaths, sternal bursa, conjunctiva, chins, pharynx, lungs, air sacs, middle ear, bone marrow and brain. Given the variability in the pathogenicity of the strains and the resistance of birds, pasteurellosis presents a great clinical and lesional polymorphism. The acute form can be devastating. (See Article: How many hens to have per square meter?)

  • When the evolution is less brutal, we observe an intense prostration
  • hyperthermia, the crest and the chins are purple. Death occurs in 3 to 6 hours.
  • Abundant yellow-green diarrhea
  • sudden loss of appetite, almost total
  • shortness of breath
  • severe thirst (high fever)
  • cyanotic head ornaments
  • hypertrophic and hot joints
  • Birds lose weight rapidly
  • Chronic cholera carriers have swollen eyes, hypertrophied chins and faces (similar to cases of coryza)
  • we can notice a thick jetage.

The lesions resulting from these Avian Cholera infections are generally characterized by bacterial colonization with necrosis, fibrinous-purulent exudate and fibroblasts in varying degrees. Diagnosis depends on isolation and identification of the responsible organism. Excessively acute form: sudden onset of disease, high mortality rate. Lesions may be completely absent; a positive diagnosis is only possible by isolation and identification of the responsible germ in the laboratory.Acute and chronic forms:

  • hemorrhage in the lungs, intestines, adipose tissue and pericardium
  • duodenum is red and congested
  • the liver is enlarged, a “cooked” appearance with small grayish-white patches of yellow necrotic fragments (yolk) floating in the abdominal cavity
  • The spleen was of normal size, unlike that.
  • birds with typhoid fever, chronic cholera carriers may have swollen quills and face, and a laboratory examination should include isolation and identification of Pasteurella from the liver.

Diagnosis

Fowl cholera (fowl pasteurellosis) is a common avian disease that can affect all types of birds and is often fatal. In the acute form, fowl cholera is one of the most virulent and contagious diseases of poultry. Diagnosis depends on the identification of the responsible P. multocida bacterium, after isolation of birds with symptoms and lesions characteristic of this condition.

The diagnosis of suspicion can be based on the observation of characteristic symptoms and lesions and on microscopic evidence of bacteria showing bipolar staining from the blood extension or tissue layers such as liver or spleen . Attenuated forms of the disease can be observed. All species of birds are susceptible to P. multocida, although turkeys may be the most affected.

Clinical Diagnosis

Avian Cholera may be suspected when there is sudden high mortality in birds by several species on a farm, especially when palmipeds are the first to be affected. Autopsy cannot provide confirmation, even when liver spots are observed, associated with damage to the heart and intestine.

Differential diagnosis

It affects many conditions. Pasteurellosis should be distinguished from avian influenza, Newcastle disease, avian salmonellosis, duck plague, cardiac petechiae in a force-fed mulard duck ENVT, poultry and swine farm clinic infectious rhinotracheitis (metapneumovirus infection) and turkey mullet, as well as all respiratory disorders.

Laboratory diagnosis

P. multocida avian cholera is isolated from bone marrow, liver, heart blood, localized lesions, nasal passages. Antibiotic susceptibility testing is often required to define the antibiotic sensitivity profile. Serological tests (ELISA) are of limited interest. At most they are indicated for rough monitoring of vaccine response.

Treatment

Treatment of Sulfaquinoxaline and other sulfonamides mixed in feed or drinking water will prevent mortality in acute cases; complete cleaning and disinfection of premises and

Treatment is applied for at least 5 days, and should be adapted according to the results of the antibiotic sensitivity test. Sanitary prophylaxis is difficult to apply. It consists of eliminating sources of P. multocida (sick or convalescent birds, rats, other birds), to prevent contamination of food and drinking water, to avoid species mixtures, age.

Medical prophylaxis consists of chemoprevention andThe risk of seeing a new virus that can be transmitted from person to person must be taken into account.

A virus that would escape from our immune system

The emergence of an Avian Cholera virus belonging to a viral subtype totally unknown to the human population, such as H5N1, renders ineffective the immune memory of the general population generated during seasonal epidemics due to classical influenza viruses (currently for types A: H3N2 and A (H1N1) pdm09). This is in favor of a pandemic, a rapid and worldwide spread of the virus.

Likely scenarios of the emergence of a new subtype

  • The first possibility is that the circulation of a virus subtype circulating in the human population will stop for several years, but the virus will remain in an animal population. In this case, if the animal population is in direct contact with a human being, it will be able to transmit the virus again. For example, the H1N1 subtype that caused the Spanish flu disappeared from the human population around 1957. However, it remained in pigs, which allowed it to reappear in humans 20 years later, in 1977.
  • The second possibility is that a viral subtype is re-created by genetic reassortment.Such a phenomenon occurs when a host co-infects with two different viruses, in this case an avian virus and a virus that infects mammals (man). In the same cell, the two viruses will multiply, producing many copies of their genomes. By assembling new viruses, mosaic viruses will form that have randomly incorporated segments of the genomes of both parental viruses. If one of these new viruses has segments of the H5 and N1 proteins, specific for the avian virus, it will completely escape recognition by the human immune system. If it also has genes that allow it to multiply effectively in mammals, then it will have the ability to transmit from man to man as effectively as “classical” influenza.

Prevention

The World Health Organization (WHO) stresses the importance of monitoring outbreaks in poultry and migratory bird populations and respiratory disease in people exposed to infected poultry in response to the risk of an influenza pandemic, promptly taking the control measures recommended by the Food and Agriculture Organization of the United Nations (FAO) and the World Organization for Animal Health (OIE), and identifying viruses in reference laboratories.

Hygiene measures

The Avian Cholera virus is usually spread through contact with infected birds. One of the main safety measures to contain the disease is therefore to observe good hygienic practices (regular hand washing, wearing a mask).

Treatments

A vaccine to prevent Avian Cholera disease. Every year, the pharmaceutical industry produces vaccines directed against the latest strains of human influenza viruses. For countries in the northern hemisphere, WHO decides on the composition of these vaccines in February, so that the vaccines are available in October, before the start of the new influenza season. WHO also launched an initiative for the development of an “anti-pandemic” vaccine. This candidate vaccine, still under development, is derived from a strain isolated in Vietnam in 2004. However, it poses many problems, the most important of which is that the pandemic virus does not yet exist.

The epidemiological surveillance orchestrated by the WHO to verify the evolution of the most recent strains of the H5N1 virus does not affect the effectiveness of the vaccine as was the case in 2004, which was signed the off development of a vaccine manufactured from a strain of 2003, and the resumption of the vaccine program from a strain isolated in 2004. In any case, it takes between 6 and 8 months to develop a vaccine, so the importance of antiviral treatments to combat the pandemic at the beginning.

Vaccination involves the introduction into the body of an agent (virus, bacterium or molecule) that will sensitize the immune system, without being pathogenic. The vaccinated subject specializes in some of these cells and manufactures antibodies against these foreign molecules. During subsequent infection with the same agent, the body will be able to fight the infection.

Antivirals

Although there is no vaccine today, there are two antivirals effective against “classical” or avian influenza viruses. These molecules inhibit the activity of an enzyme of the virus, neuraminidase. They can be used in curative treatment and one of them as a preventive treatment. In the context of the pandemic, these antivirals are mainly used to protect health personnel and professions whose maintenance of activity is essential to ensure the functioning of national structures. It is worth remembering that antibiotics are inactive against viruses and that their use is only recommended in case of bacterial superinfection.