Todayโs path rounds are on ๐๐ข๐ฌ๐ญ๐จ๐ฉ๐ก๐ข๐ฅ๐ฎ๐ฌ ๐ฌ๐จ๐ฆ๐ง๐ข!
๐๐ก๐๐ญ ๐ข๐ฌ ๐ข๐ญ?
๐๐ข๐ฌ๐ญ๐จ๐ฉ๐ก๐ข๐ฅ๐ฎ๐ฌ ๐ฌ๐จ๐ฆ๐ง๐ข is a bacterial disease of cattle that can cause a wide range of lesions throughout the body! Its primary role is as a respiratory pathogen, however.
๐๐ก๐จ ๐ ๐๐ญ๐ฌ ๐ข๐ญ?
Cattle primarily get this disease, specifically cattle on feedlots in North America.
๐๐จ๐ฐ ๐๐จ ๐๐ง๐ข๐ฆ๐๐ฅ๐ฌ ๐ ๐๐ญ ๐ข๐ง๐๐๐๐ญ๐๐?
Histophilus somni is considered to be a ๐๐จ๐ฆ๐ฆ๐๐ง๐ฌ๐๐ฅ ๐๐๐๐ญ๐๐ซ๐ข๐ in the mouth of cattle, meaning it is normally found there and generally does not cause issues. However, when cattle are stressed, the inhaled bacteria may gain access to the bloodstream and spread throughout the body, causing a ๐ฌ๐๐ฉ๐ญ๐ข๐๐๐ฆ๐ข๐ (bacteria replicating in the blood). The most common cause of stress leading to this disease is cattle moving to the feedlot, where they comingle with all kinds of cows from all kinds of places and need to sort out their herd structure.
๐๐ก๐ฒ ๐ข๐ฌ ๐ญ๐ก๐ข๐ฌ ๐ ๐ฉ๐ซ๐จ๐๐ฅ๐๐ฆ?
As mentioned before, this bacteria will cause a septicemia, which distributes the bacteria far and wide throughout the cow. It primarily lodges in the ๐ฉ๐ฅ๐๐ฎ๐ซ๐ (covering of the lungs), heart, ๐ฉ๐๐ซ๐ข๐๐๐ซ๐๐ข๐ฎ๐ฆ (covering of the heart), joints and even the brain.
In these areas, the bacteria adheres to the lining of blood vessels causing damage, and producing small ๐ญ๐ก๐ซ๐จ๐ฆ๐๐ข (blood clots). These thrombi block blood flow within the vessel, causing areas of ๐ข๐ง๐๐๐ซ๐๐ญ๐ข๐จ๐ง (tissue death due to lack of blood flow). Depending on the tissue, these infarcts can have different effects, but ultimately this disease usually leads to death for the cow.
๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐๐ข๐๐ ๐ง๐จ๐ฌ๐๐?
Typically, sudden death is the first clinical sign identified in a group of cattle. Depending on which tissues the bacteria lodged itself in, you may also see difficulty breathing, ๐ง๐๐ฎ๐ซ๐จ๐ฅ๐จ๐ ๐ข๐ ๐ฌ๐ข๐ ๐ง๐ฌ like falling down or stumbling, lameness and swollen joints, or even unwillingness to move. Based on these clinical signs, and completing an on-farm necropsy, the veterinarian can make the diagnosis.
At necropsy, we see the results of the bacteria causing infarcts in multiple tissues. We can see ๐๐ข๐๐ซ๐ข๐ง๐จ๐ฎ๐ฌ ๐ฉ๐ฅ๐๐ฎ๐ซ๐ข๐ญ๐ข๐ฌ or ๐ฉ๐๐ซ๐ข๐๐๐ซ๐๐ข๐ญ๐ข๐ฌ (inflammation with release of the stringy material blood clots are made of), pale areas of dead muscle within the heart, and ๐ฉ๐จ๐ฅ๐ฒ๐๐ซ๐ญ๐ก๐ซ๐ข๐ญ๐ข๐ฌ (inflammation of multiple joints). We can also see multiple small hemorrhages in the brain due to infarction. To confirm the diagnosis, PCR or bacterial culture can be done on tissue samples taken at necropsy to detect the bacteria.
๐๐จ๐ฐ ๐ข๐ฌ ๐ข๐ญ ๐ญ๐ซ๐๐๐ญ๐๐?
Usually this disease is treated with very strong antibiotics, however treatment is not always successful. Antibiotics usually need to be given early on in the course of the disease, before massive amounts of infarction has occurred, so having knowledgeable staff on farm who can identify sick cattle is crucial.
๐๐ก๐จ๐ญ๐จ๐ฌ
1) Lungs with fibrinous pleuritis. Pathologists often describe this as a โbread and butterโ appearanceโฆ i.e. you dropped a piece of bread with butter on it, and when you pick it up it has fine globs of butter sticking up. Gross.
2) Fibrinous pericarditis showing similar bread and butter around the heart.
3) A pale infarction in the heart muscle.
4) A joint with arthritis from the bacteria.
5-6) Examples of hemorrhage within the brain from the bacteria.
๐๐จ๐ฎ๐ซ๐๐๐ฌ
Maxie, G. Jubb, Kennedy and Palmerโs Pathology of Domestic Animals, Volume 2. Sixth Edition.
Janzen, E.D. Histophilosis. Merck Veterinary Manual, 2020.
Photos 1-6 courtesy of University of Calgary Diagnostic Services Unit.
