Histophilosis, or Histophilus somni–associated disease, is a common disease in North American cattle. It also has been reported to occur sporadically in beef. Histophilus somni is a Gram-negative bacterium that is associated with a disease complex (termed histophilosis) that can produce several clinical syndromes. Histophilus somni (H. somni) is a Gram-negative bacterium currently classified as a member of the Hae- mophilus-Actinobacillus-Pasteurella group. Clinical.

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They are given an injection of a long-acting antibiotic that is designed to protect them against infection in the early, most stressful time at the feedlot. Although this band is faint in the depicted profiles of the four bighorn isolates, it was more clearly defined in other blots.

This organism has also been isolated from tonsillar and reproductive tract samples from American bison None of the tissue sections were immunohistologically positive for M. Involvement of the central nervous system, whereby blood flow to the spinal cord and brain is affected, results in a syndrome histpphilus as thromboembolic meningoencepahlitis TEME.

Histophilus somni (Haemophilus somnus) Complex | Zoetis US

Respiratory disease and poor lamb recruitment have been identified as limiting factors for bighorn-sheep populations. These lambs had been submitted for necropsy after sudden illness or death, with or without prior depression, stiffness, or fever. AndersonPatrick J.

Essentially all bighorn sheep populations harbor multiple somn of Pasteurellaceae 15and Pasteurella or Mannheimia spp.

Histophilus somni

Young growing cattle age months are most commonly infected and show clinical signs. Finally, immunohistochemistry may be used to identify H. Selective culture media is needed to ensure growth of the bacteria and samples should ideally be taken from untreated animals. Pasteurella and Mannheimia spp.


In contrast, the lower rMW bands were approximately 38 kDa in the isolates from the cattle and domestic sheep but were quite variable in the bighorn-sheep isolates.

In the heart this can cause myocarditis with multiple infarcts, necrosis, and abscessation. All these sheep were considered to be clinically healthy, but poor lamb recruitment was noted in the Pancake Range population. Identification and source of Haemophilus somnus isolates in the United States and Canada in this study. Transferrin receptors on ruminant pathogens vary in their interaction with the C-lobe and N-lobe of bovine transferrins. The advanced consolidation in the anterior lobes histophiluus that the lesions could have been 5 to 7 d old.

Pathogenic or nonpathogenic H. Immunohistochemical study with antibody specific for H. The mucosa was exposed by spreading the preputial or vulvar orifice. Although all but 1 of the bighorn isolates and 2 of the domestic-sheep isolates produced identical biochemical utilization reactions that were characteristic of biovariant 4, the bighorn-sheep isolates lacked the yellow pigmentation and CO 2 requirement of the domestic-livestock isolates.

The 12 males M and 62 females F were approximately 8 mo to more than 4 y of histophiljs. The kDa antigen was not present in bovine isolate Pt but was variably detectable in the other isolates.

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It is clear, however, that nonhemolytic H. Therefore, acute and convalescent titers are needed to make a definitive diagnosis which is often times impossible due to the rapid course of the disease. Lack of these cardinal characteristics, as described for domestic-livestock hisotphilus 10could result in lack of detection and identification of the organism.


The most striking gross lesions will be seen in cattle with either myocarditis or respiratory disease. Histophilus somni myocarditis in a beef rearing calf in the United Kingdom.

In 1 study, rams in 22 Serology may also be used to make a definitive diagnosis of H. Radostits OM et al. Isolate identification a Geographic location Animal species; b anatomic site Associated clinical condition A.

Treatment is often unsuccessful when antibiotic therapy is delayed or if the animal is already recumbent. The bacteria require a breakdown in mucosal immunity in order to cause disease. Haemophilus somnus recently reclassified as Histophilus somni is associated with respiratory disease in American bison, domestic sheep, and cattle.

Whether the vaginal isolates from bighorn sheep in the Muddy Mountain population were associated with poor reproductive performance is unknown.

Colonies characteristic of Pasteurellaceae were further tested.

Oxytetracycline has been effective in the treatment of TME when the drug is given at the onset of clinical signs. Respiratory infection often precedes infection of other organ systems.

Growth of these organisms can be obscured by the multiple bacterial species that constitute the normal flora of the upper respiratory tract of ruminants.

If calves are to be vaccinated it should be performed prior to entry into the feedlot. The histopathologic findings in the pneumonic lungs of the bighorn sheep were more consistent with the more chronic pneumonia detected in the d bovine experiment and in clinical smni.