Histophilosis in Cows: Respiratory, Nervous, and Septicemic Disease
- See your vet immediately if a cow has fever, sudden depression, hard breathing, collapse, blindness, circling, seizures, or goes down unexpectedly.
- Histophilosis is caused by the bacterium Histophilus somni and can show up as pneumonia, thromboembolic meningoencephalitis (brain disease), septicemia, myocarditis, arthritis, or sudden death.
- Recently transported, stressed, commingled, or feedlot cattle are at higher risk, especially when bovine respiratory disease pathogens are also present.
- Fast treatment matters. Early cases may respond to labeled antimicrobials and supportive care, but nervous-system disease and septicemia can become fatal very quickly.
- Typical 2026 U.S. cost range is about $75-$250 per affected animal for field evaluation and first-line treatment, with herd outbreaks, repeat treatments, diagnostics, or intensive nursing often increasing total costs to $300-$1,000+ per animal.
What Is Histophilosis in Cows?
Histophilosis is a bacterial disease complex caused by Histophilus somni. In cattle, it is best known for causing sudden, severe illness involving the lungs, bloodstream, brain, heart, joints, or several body systems at once. Your vet may also use the term H. somni-associated disease. In North America, it is a well-recognized cause of illness in feedlot cattle, but beef and dairy cattle in other settings can be affected too.
One of the most serious forms is thromboembolic meningoencephalitis, often shortened to TEME. This happens when the infection damages blood vessels and affects the brain and spinal cord. Affected cattle may become dull, blind, uncoordinated, stiff, or suddenly unable to rise. Other cattle show mainly respiratory disease, with fever, depression, nasal discharge, and pneumonia-like signs.
A frustrating part of histophilosis is how fast it can move. Some cattle look mildly off feed at first, then worsen over hours rather than days. Others are found dead with very little warning. Because of that speed, early veterinary involvement is one of the most important parts of care.
Symptoms of Histophilosis in Cows
- Fever
- Depression, droopy attitude, or separation from the group
- Reduced appetite or sudden off-feed behavior
- Fast breathing, cough, or labored breathing
- Nasal discharge
- Stiff gait or reluctance to move
- Circling, head pressing, blindness, or abnormal behavior
- Sudden collapse, paddling, seizures, or inability to stand
- Sudden death
- Lameness or swollen joints in some cases
Histophilosis can look like other cattle diseases at first, especially shipping fever, listeriosis, polioencephalomalacia, or other causes of septicemia. What raises concern is the combination of fever plus rapid decline, or any neurologic signs such as blindness, circling, collapse, or seizures. See your vet immediately if a cow is down, struggling to breathe, or worsening over the same day.
What Causes Histophilosis in Cows?
Histophilus somni is a gram-negative bacterium that can live on normal bovine mucous membranes, especially in the respiratory and reproductive tracts. That means some cattle may carry the organism without looking sick. Disease tends to happen when stress, viral infection, crowding, transport, weather shifts, or mixing cattle from different sources gives the bacteria an opening to invade deeper tissues.
This is why histophilosis is often discussed as part of the broader bovine respiratory disease complex. Viral infections such as IBR, BRSV, or PI3, along with other bacteria like Mannheimia haemolytica and Pasteurella multocida, can damage airway defenses. Once that happens, H. somni may contribute to pneumonia, septicemia, or vascular injury that leads to brain and heart lesions.
Risk is often highest in recently weaned, transported, or feedlot cattle, but outbreaks can also occur in other groups. Poor ventilation, mud, dust, nutritional stress, abrupt ration changes, and delayed recognition of early illness can all make a herd more vulnerable. Your vet can help identify which stressors matter most on your operation.
How Is Histophilosis in Cows Diagnosed?
Diagnosis starts with history and pattern recognition. Your vet will look at age group, recent transport or commingling, vaccination status, fever, respiratory signs, neurologic signs, and how quickly cattle are declining. Because histophilosis overlaps with several other serious diseases, diagnosis usually involves ruling out look-alikes while deciding whether treatment needs to start right away.
On-farm workup may include a physical exam, rectal temperature, lung assessment, and evaluation of gait, mentation, vision, and cranial nerve function. In some cases, your vet may recommend bloodwork, PCR or culture from appropriate samples, or necropsy with tissue testing if a cow dies. Isolation of H. somni from sterile sites such as blood, cerebrospinal fluid, brain, joint fluid, or internal organs is more meaningful than finding it on mucosal surfaces, because the organism can be a normal resident there.
Necropsy can be especially helpful in herd outbreaks. Histopathology and laboratory testing may confirm vascular damage, pneumonia, myocarditis, or brain lesions consistent with histophilosis. Even when a single live animal cannot be definitively confirmed in the field, herd-level diagnosis often becomes clearer when your vet combines clinical signs, response to treatment, and postmortem findings.
Treatment Options for Histophilosis in Cows
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Prompt farm exam by your vet or herd treatment protocol review
- Early treatment of mildly affected cattle with a labeled antimicrobial selected by your vet
- Anti-inflammatory medication when appropriate and legal for the class of cattle
- Isolation in a dry, low-stress pen with easy access to water and feed
- Temperature monitoring and close recheck over the next 24-48 hours
Recommended Standard Treatment
- Full veterinary exam plus treatment plan for the individual cow and the exposed group
- Labeled long-acting antimicrobial therapy chosen by your vet based on likely pathogens, withdrawal times, and operation goals
- Anti-inflammatory therapy and supportive care
- Targeted diagnostics such as necropsy, sample submission, or herd-level testing when indicated
- Review of vaccination timing, receiving protocols, ventilation, stocking density, and pen management
Advanced / Critical Care
- Emergency veterinary assessment for down cattle, severe respiratory distress, or neurologic disease
- Repeated treatments, intensive nursing care, fluids or other supportive measures when feasible
- Expanded diagnostics including necropsy, histopathology, culture, PCR, and differential testing for other neurologic or septicemic diseases
- Herd outbreak investigation with prevention redesign for receiving, vaccination, and biosecurity protocols
- Referral-level consultation or intensive individual management for high-value breeding stock when practical
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Histophilosis in Cows
Bring these questions to your vet appointment to get the most out of your visit.
- Does this look most consistent with histophilosis, or are diseases like listeriosis, polio, or other respiratory infections also likely?
- Which cattle should be treated right now, and which ones need closer monitoring or separation from the group?
- What antimicrobial options are appropriate for this class of cattle, and what withdrawal times do I need to follow?
- Are the neurologic signs severe enough that prognosis is poor, even with treatment?
- Would necropsy or lab testing on a fresh death help confirm the diagnosis and guide herd decisions?
- Should we change our receiving, vaccination, commingling, or metaphylaxis protocols for future groups?
- Are ventilation, mud, dust, bunk space, or ration changes increasing disease pressure here?
- What signs mean I should call you back immediately in the next 12-24 hours?
How to Prevent Histophilosis in Cows
Prevention focuses on lowering stress and strengthening herd respiratory health before cattle are challenged. Work with your vet on a receiving plan that covers vaccination timing, low-stress handling, clean water access, nutrition, parasite control, and early identification of sick animals. In U.S. feedlots, vaccination against Histophilus somni is common, but vaccine choice and timing still need to match the age, source, and risk level of the cattle.
Good prevention also means reducing the conditions that let respiratory disease spread. That includes avoiding overcrowding, improving ventilation, limiting dust and mud, and minimizing abrupt mixing of cattle from different sources when possible. Newly arrived or recently weaned cattle should be watched closely for fever, droopiness, reduced intake, or subtle breathing changes.
During an outbreak, prevention becomes herd management as much as medicine. Your vet may recommend changes to treatment thresholds, pen pulls, vaccination strategy for future groups, and in some operations, metaphylaxis for high-risk arrivals. Because histophilosis often travels with the broader bovine respiratory disease complex, the best prevention plan usually addresses the whole system rather than one bacterium alone.