Eugene
University of Calgary, Canada
Title: he changing clinical manifestations and pathological processes Histophilus somni infections in cattle
Biography
Biography: Eugene
Abstract
Histophilus somni, a small, pleomorphic, Gram-negative bacteria, causes an infection commonly referred to as “Histophilosis”,
implying that the infection is systemic even though the clinical manifestation may be specific to an organ system. It was first
identified in 1960 as the cause of infectious thromboembolic meningoencephalitis (ITEME) in cattle fed in confinement and this
encephalitic form of the infection was recognized to be the main manifestation. More recently, this manifestation is diagnosed less
commonly and infection with H. somni has been shown to be an important cause of sporadic “sudden death” in groups of recently
weaned, confined cattle and associated with diverse pathological processes involving the heart, thoracic space and lungs. Modern
microbiology has demonstrated and continues to demonstrate characteristics of the organism that contribute significantly to its’
virulence but may not be present in all isolates. Pathogenic and commensal strains have been shown to exist. The diagnosis of
Histophilosis historically was made by isolating the pathogen microbiologically which was often difficult because of prior treatment
with antimicrobials. However, confirmation currently is made using molecular techniques like immunohistochemical (IHC) staining
of H&E fixed tissues or polymerase chain reaction (PCR) of fresh swabs taken from the lesions. In vitro examination of the organism
suggests it is sensitive to most antibiotics, although the minimum inhibitory concentration (MIC) needed to prevent growth of H.
somni has apparently increased in recent years. The various clinical and pathological manifestations will be discussed with emphasis
on diagnosis and complications of clinical management.