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Humoral immunity in experimental thromboembolic meningoencephalitis in cattle caused by Haemophilus somnus
Abstract:
Of 23 cattle inoculated IV with Haemophilus somnus, 16 (70%) died of thromboembolic meningoencephalitis. The inoculum was prepared from a minimally subcultured isolate of H somnus that was passaged through a calf by intracisternal inoculation immediately before use. Serum antibody titers, as measured by 7 serologic tests, were not correlated with the animal's susceptibility to infection. All cattle that died had a mean 4-fold increase in agglutination titer during the acute phase of the disease, 2 to 4 days after inoculation. Similarly, high acute-phase titers were demonstrated in 15 cattle with naturally occurring disease. Haemophilus somnus was isolated more frequently and in greater numbers from the CNS and urinary tract than from other organs of cattle that died.
Insights
A study found that 70% of cattle inoculated with Haemophilus somnus died from thromboembolic meningoencephalitis. Antibody titers did not predict susceptibility, but increased during the acute phase of the disease.
Area of Science:
- Veterinary Pathology
- Bovine Infectious Diseases
- Microbiology
Background:
- Thromboembolic meningoencephalitis (TME) is a severe disease in cattle.
- Haemophilus somnus is a significant pathogen implicated in bovine respiratory and reproductive diseases.
- Understanding the pathogenesis and host response to H. somnus is crucial for disease control.
Purpose of the Study:
- To investigate the pathogenicity of Haemophilus somnus in cattle.
- To evaluate the correlation between serum antibody titers and susceptibility to H. somnus infection.
- To identify the primary sites of H. somnus replication during acute infection.
Main Methods:
- Cattle were inoculated intravenously with a prepared isolate of Haemophilus somnus.
- Serum antibody titers were measured using seven serologic tests.
- Post-mortem examination and microbial isolation from various organs were performed on deceased animals.
Main Results:
- 16 out of 23 (70%) inoculated cattle died from thromboembolic meningoencephalitis.
- Serum antibody titers showed no correlation with susceptibility to infection.
- A mean 4-fold increase in agglutination titer was observed during the acute phase (2-4 days post-inoculation) in cattle that died.
- Haemophilus somnus was frequently isolated from the central nervous system (CNS) and urinary tract.
Conclusions:
- Haemophilus somnus can cause fatal thromboembolic meningoencephalitis in cattle via intravenous inoculation.
- Acute-phase antibody response, rather than pre-existing titers, may be indicative of active infection.
- The CNS and urinary tract are significant sites for H. somnus replication during acute disease.