Histophilus somni

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Histophilus somni
Systematics
Department : Proteobacteria
Class : Gammaproteobacteria
Order : Pasteurellales
Family : Pasteurellaceae
Genre : Histophilus
Type : Histophilus somni
Scientific name of the  genus
Histophilus
Angen et al. 2003
Scientific name of the  species
Histophilus somni
Angen et al. 2003

Histophilus somni (formerly Haemophilus somnus ) is a Gram-negative bacterium that has been a new species of the Pasteurellaceae family since 2003, which has beengrouped togetheras Haemophilus agni , Histophilus ovis and Haemophilus somnus .

morphology

There are pleomorphic , yellowish rods that are immobile and do not form spores. In the gram color they turn red (they are gram negative ).

Culture

Growth condition: optional anaerobic / microaerophilic .

Usually shows no hemolysis .

biochemistry

  • Catalase : negative (no bubbles)
  • Oxidase : delayed positive (blue)
  • X or V factor: no dependency
  • Urease : negative (yellow)
  • H 2 S : negative (no blackening)

Virulence factors

Virulence factor Mode of action
Adhesion protein Formation of a fibril network which is surrounded by immunoglobulin-binding proteins
Lipooligosaccharides (LOS) - no O-side chains example
example - the core oligosaccharide is more complex than LPS → Inflammatory reaction → Cytokines are released when the CD14-LPS complex binds to TLR.
example - due to a phase variation, different epitopes are formed (not in the case of a subclinical course) → Protection against the body's own immune response

→ Resistance to the compliment system

Lipid A Endotoxin
Transferrin iron complex Via transferrin-binding protein (membrane)
histamine
Exotoxin
Induction of apoptosis

meaning

ISTMEM (infectious septicemic-thrombosing meningoencephalomyelitis) - sleeper syndrome in cattle (especially in cattle aged six to twelve months). Worldwide distribution, but mainly in countries with farms with large herds of cattle (e.g. USA and Canada).

clinic

Histophilus somni is an opportunist who, in the case of mucosal immunodeficiency due to e.g. B. transport stress or a viral infection can lead to serious clinical pictures. In healthy cattle and sheep, the pathogen is mainly detectable in the prepuce or vagina, and in cattle also in the upper respiratory tract.

The pathogen has a low tenacity and transmission from cattle to cattle occurs via direct contact or droplet transmission .

Histophilus somni can lead to three different courses of disease:

  • respiratory
  • central nervous system
  • septicemic

The disease generally has a rapid course.

Histophilus somni is part of the enzootic bronchopneumonia ( Bovine respiratory Disease Complex ), also known colloquially as the bovine flu complex . Acute laryngitis , pneumonia or tracheitis indicate a respiratory or septicemic course of the disease. The latter often leads to arthritis . Peracute septicemia can sometimes develop after 12 to 36 hours , regardless of whether respiratory symptoms were previously visible or not. This can lead to central nervous disorders.

The general condition worsens rapidly and there is fever, fatigue, ataxia , paresis to paralysis , the animals lying on their side with a stretched position, somnolence , coma and ultimately death. The clinical symptoms are unspecific with putrid bad breath and cough.

The bacterium has been associated with ISTMEM in beef cattle in Canada and the USA since 1956. The problem has also occurred in individual cases in Germany since 1975, but does not play such a major role as it does on the North American continent.

If an animal falls ill with ISTMEM, death can occur within 24 hours.

If the genital tract is affected, the consequences are abortions , chronic, purulent endometritis , infertility and calves with a weak life.

If the disease is septicemic, the bacteria enter the bloodstream. There they cause apoptosis of the endothelial cells, which in turn leads to vasculitis and thrombosis. Histophilus somni enters the brain with the blood , where neutrophil granulocytes infiltrate and tissue necrosis occurs. If the pathogen gets into the heart, it causes myocarditis with multiple infarcts, necrosis and abscess formation. This is shown clinically and a. a right heart defect, mouth breathing and coughing.

In sheep, septicemia, mastitis , epididymitis and, experimentally, meningitis can occur.

Diagnosis

High animal density, new purchases or weather changes are predisposing factors that can be recorded in the anamnesis. The clinical findings also contribute to the diagnosis. ISTMEM is suspected when a respiratory disease leads to a central nervous disease or is (suddenly) fatal.

The sampling depends on the clinic and the test material may be. a. can be obtained from blood, CSF, joints, brain, pleural fluid, liver or kidney.

The most important procedure in diagnostics is the pathogen detection through cultivation. Cultivation is best carried out on complex, nutrient-rich culture media with a CO 2 tension of five to ten percent. Further Selektivnärmedien used.

Other methods are serology and immunohistochemistry . The serology is too slow in practice, as one needs a titer for both acute and convalescent cases.

Differential diagnosis

Course of disease Differential diagnosis
respiratory DHV1 , malignant catarrhal fever , BRSV , pasture emphysema
central nervous system Listeriosis , rabies , lead poisoning , cerebral necrosis (vitamin B1 deficiency), septicemic MEM

Pathogenesis

Early infection phase : The exopolysaccharides , biofilm formation , LOS and OMPs lead to colonization in the host. Induction of apoptosis and binding of iron transferrin promote growth. Histamine leads to edema and increased mucus production, which in turn leads to bronchoconstriction and vasoconstriction . LOS attracts inflammatory cells via chemotaxis and vasculitis and thrombosis occur .

The bacterium kills macrophages within 24 hours and causes a massive influx of inflammatory cells into the tissue. In severe cases this causes necrosis and the formation of many H. somni -specific IgEs . About the hypersensitivity type I it comes to anaphylactic or allergic reaction.

pathology

Changes are mainly seen in myocarditis and the respiratory disease course. With myocarditis, the free wall of the left ventricle appears pale in all its thickness. Respiratory diseases lead to pulmonary edema, congestion and fibrinous pleurisy.

ISTMEM is difficult to understand macroscopically. Vasculitis, neutrophilic inflammation and tissue necrosis of the affected organs can be detected microscopically.

therapy

Antibiotics such as penicillin , sulfonamide , flfenicol and oxytetracycline (good results with ISTMEM if given immediately at the first clinical signs) are effective. The success of the treatment depends very much on how early the treatment is started.

prophylaxis

In principle, preventive measures are difficult because the pathogen occurs ubiquitously .

Vaccinations are mainly against ISTMEM, but the success of the vaccination is controversial. It is usually not carried out in Germany as there are only a few outbreaks. In the USA it is used more, because Histophilus somni occurs much more frequently there and there are sometimes 100% positive herds.

The examination of insemination bulls before they are used for breeding purposes can severely limit the spread.

literature

  • Veterinary microbiology, infection and epidemic science ; Hans-Joachim Selbitz, Uwe Truyen, P. Valentin-Weigan; 2010, 9th, completely revised edition; ISBN 978-3-8304-1080-5

Individual evidence

  1. ↑ Carlton L. Gyles et al. : Pathogenesis of Bacterial Infections in Animals. John Wiley & Sons, 2010, ISBN 978-0813812373 , pp. 388-389.

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