DOMESTIC EQUINES · OWNER EDUCATION
Strangles in Horses
Strangles is a contagious bacterial respiratory disease that commonly causes fever, nasal discharge and swollen lymph nodes.
THE SHORT VERSION
What matters for your animal?
Start with the warning signs and when-to-contact sections if your animal is unwell. The same outward change can have several causes, so this guide helps you prepare questions rather than identify a diagnosis on your own.
What is this condition?
Strangles is a contagious bacterial respiratory disease that commonly causes fever, nasal discharge and swollen lymph nodes. The same outward signs can occur with several diseases, so an examination and appropriately selected testing are important.
Strangles is an infectious disease with implications for contact equines, equipment, and movement as well as care of the affected animal. Swellings or discharge need appropriate sampling and interpretation. Biosecurity decisions may continue after an animal seems better. Keep a record of contacts, arrivals, and affected animals, and ask the veterinarian how clearance and return to normal activity will be established.
Which species does this guide cover?
The species listed above are the focus of this guide, rather than a complete list of every animal that can develop this condition. Causes, testing and treatment may differ between species and individual patients.
Why can it happen?
- Streptococcus equi spread by direct contact or contaminated hands, equipment, water and surfaces.
- Recovered horses can occasionally carry and spread the organism.
An infectious illness depends on both the organism and the animal's ability to resist it. Exposure does not always produce the same severity of illness in every animal. Age, previous immunity, nutrition, stress, and concurrent disease can influence the outcome. The infection may also cause complications that need treatment separately from the organism itself. For example, correcting fluid loss or supporting breathing can be essential even when a targeted medicine has already been started.
What might an owner notice?
- Fever, thick nasal discharge and painful swelling under the jaw or throat.
- Difficulty swallowing, reduced appetite or noisy breathing.
Breathing effort is often more important than the sound an animal makes. Watch for increased work of the chest or abdomen, an unusual posture, inability to settle, or a change from that animal's normal pattern at rest. A quiet animal may still be struggling. If breathing is difficult, repeated handling can add stress and worsen the situation. Contact the appropriate veterinary service promptly and follow transport instructions rather than spending time trying to identify the cause at home.
The number affected and the sequence of cases can provide important clues. Record which animals or colonies changed first, whether they share feed, water, housing, equipment, or recent contacts, and any deaths. One patient's improvement does not establish that the shared cause has been removed. A group investigation may require different samples or visits from the care of one visibly affected animal. Avoid moving animals or materials between groups while a potentially transmissible problem remains unresolved.
How is the problem investigated?
Examination plus polymerase chain reaction or culture from an appropriate sample. Further evaluation when complications or a carrier state is suspected.
Molecular testing, such as PCR, looks for genetic material from a target organism in the submitted sample. It can be useful, but the meaning depends on the sample site, timing, and disease. Detecting material is not always the same as proving that the organism explains every sign, while a negative result may not exclude infection if sampling or timing was unsuitable. The veterinarian interprets the result alongside the examination and other findings rather than treating it as an isolated verdict.
What might treatment involve?
Isolation, supportive care and complication management. Antibiotic decisions depend on disease stage and individual risk.
Antibiotic selection depends on the suspected or confirmed bacteria, the site of infection, and the animal's safety needs. A culture identifies organisms that grow from a sample; susceptibility testing helps assess which medicines may work against them. The laboratory result is considered alongside tissue penetration, dosing feasibility, and the clinical response. Antibiotics do not treat viruses, and adding one without a clear reason can obscure the investigation or cause adverse effects. Follow the current prescription rather than using leftovers from a previous illness.
This is an overview, not a prescription or a recommendation for a specific individual animal.
What can owners do at home?
Write down when the problem began and track appetite, drinking, waste, activity, breathing and medication use. Bring clear photos or short videos when they can be taken without stressing the animal. Follow the veterinary team's instructions for medication, feeding, isolation, environmental changes and rechecks.
Avoid actions that could make care less safe.
- Do not use human medication, leftover antibiotics or another animal's treatment without veterinary direction.
- Do not force food or water into an animal that cannot swallow normally, is struggling to breathe or may have an obstruction.
- Do not delay veterinary care when pain, breathing, appetite, urination, movement or responsiveness changes quickly.
What can the longer-term outlook involve?
The outlook depends on the underlying cause, severity, species and how quickly effective care begins.
A recheck is not simply a repeat of the first appointment. It assesses whether the original problem is improving, whether complications are appearing, and whether the treatment remains appropriate. The useful measures may include comfort, function, intake, body weight, examination findings, or selected tests. Ask which changes are expected before the visit and which should trigger an earlier call. Improvement in one sign does not always mean that every part of the disease has resolved.
Can risk be reduced?
Provide species-appropriate nutrition, housing, sanitation and routine veterinary care. Learn the animal's normal behavior, appetite, body condition and waste pattern so meaningful changes are noticed early.
Disease prevention includes the route by which animals, people, equipment, bedding, feed, or water can carry a problem between groups. Separation works best when it also includes dedicated tools, careful handling order, and an appropriate cleaning plan. A newly arrived animal may appear well while a disease is incubating. Ask which tests or observation period suit the species and suspected disease before mixing groups. Cleaning, disinfection, and disposal requirements differ between organisms, so a single household product is not a universal solution.
When should you arrange care?
- Contact a veterinarian promptly for fever, thick nasal discharge and painful swelling under the jaw or throat. or difficulty swallowing, reduced appetite or noisy breathing..
- Arrange reassessment if signs return, worsen or do not improve as expected.
Seek urgent veterinary advice if you notice:
DO NOT DELAY URGENT CARE- Breathing obstruction, inability to swallow, severe weakness, neurologic signs or rapidly spreading swelling.
What information helps the care team?
Record which animals are affected, feeding or housing changes, recent arrivals, treatments and any losses. For a flock or herd problem, the number affected and the pattern over time may be as important as one animal's examination.
How should you understand the tests?
Ask what each proposed test is intended to answer. Some tests identify a cause; others assess severity, organ function or treatment safety. Results are interpreted with the examination and history. A normal result does not exclude every problem, and an abnormal result does not always explain every sign.
Questions to ask before leaving
- What is confirmed, and which other explanations are still being considered?
- What changes should we expect with the proposed plan, and when should we reassess if they do not occur?
- Which observations should I record, and which changes mean I should call sooner?
- What medicine or home-care problems should I report, and what are the instructions for a missed dose or suspected side effect?
- When is the recheck, what will it assess, and whom should I contact after hours?
A care plan may be adjusted as results or the response become clearer. Keep the written instructions and tell the team if cost, handling or administration difficulty makes the plan hard to follow.
Sources behind this guide
VeterinaryPartner — client education from the Veterinary Information NetworkVeterinary, university or animal-health guidance ↗American Association of Equine Practitioners: horse-owner resourcesVeterinary, university or animal-health guidance ↗Content last reviewed: September 17, 2026. Review status: veterinary-informed; independent veterinarian review not yet completed.