Fever of Unknown Origin in Cats | VCA Animal Hospital

What is a fever of unknown origin?

Fever is a term that refers to an elevated body temperature. The normal body temperature range for cats is between 100.5°F and 102.5°F (38.1°C and 39.2°C). To be classified as a fever of unknown origin (FUO), the body temperature must be above 103.5°F (39.7°C) for longer than a few days in duration, with no obvious underlying cause based on history and physical examination.

What causes a fever?

A fever is initiated by the presence of a pyrogen (a fever-producing substance). The pyrogen can be endogenous (produced from within the body) or exogenous (from the outside). This pyrogen causes the release of substances from the white blood cells (leukocytes) such as interleukin-1, interleukin-6, and tumor necrosis factor. These substances, in turn, reset the body’s “thermostat”, the temperature-regulating region located in the hypothalamus (located in the brain). This activates physiologic responses within the body to elevate the temperature.

If this is a natural process, why is it a problem?

A fever is beneficial to the body because it hampers the ability of viruses and bacteria to reproduce and improves the immune system response to foreign invaders. However, if the body temperature remains above 105°F (40.5°C) for more than a day or two, the patient becomes lethargic and anorexic, and can rapidly become dehydrated. If the temperature persists above 106°F (41.1°C), cerebral edema (swelling around the brain), bone marrow suppression, and clotting disorders (disseminated intravascular coagulation, or DIC) may develop.

“A fever is beneficial to the body because it hampers the ability of viruses and bacteria to reproduce and improves the immune system response to foreign invaders.”

When a fever persists, several consequences occur within the body. Among these are increased metabolic demands to maintain the higher temperature, which causes increased fluid and caloric requirements and increased breakdown of muscle tissues. A persistent high fever (one that lasts for more than forty-eight hours) is considered serious and potentially life threatening.

What are the clinical signs of fever of unknown origin?

Most cats with a fever are lethargic, reluctant to move, have a loss of appetite, have increased heart and breathing rates, and are dehydrated. They may also be shivering or showing stiffness. With a fever of unknown origin, these clinical signs are present but there is no obvious cause for them.

How is FUO diagnosed?

If your cat has a fever, your veterinarian will perform a thorough physical examination, looking specifically for evidence of bite wounds, lacerations, punctures, or other signs of trauma. Diagnostic blood tests will usually include a complete blood cell count (CBC), a serum biochemistry panel, feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) testing, and a urinalysis. Urine cultures are often performed to search for an underlying urinary tract infection.

Additional tests may be recommended based on your cat’s clinical signs such as feline infectious peritonitis (FIP) and Toxoplasmosis titers, blood cultures, or thyroid function tests. Diagnostic imaging (such as X-rays or ultrasound), or cytology (looking at the cell types aspirated from swellings or lumps) may also be needed to establish a firm diagnosis.

What causes FUO?

As the name suggests, this is a fever without a demonstrable cause.

Most cases of fever in cats are caused by a viral infection such as FeLV, FIV, FIP, feline panleukopenia virus, herpesvirus or calicivirus. Many viral infections will wax and wane before resolution. For example, it is common for a cat with a viral infection to seem completely well and then to experience a relapse a week or two later.

Bacterial infections can also cause a fever, but this is usually accompanied by an obvious wound or swelling. Unusual bacterial infections that are secondary to bites wounds include Yersinia, Mycobacteria, Nocardia, Actinomyces, and Brucella. The infection may be located in the chest cavity (pyothorax), the kidney (pyelonephritis), the abdominal cavity (from a penetrating intestinal injury resulting in low-grade peritonitis), in the mouth, from a tooth root abscess, etc.

Less commonly, a fever may be secondary to inflammation caused by blunt trauma, lymphoma and other tumors, or a systemic fungal infection. It is necessary to eliminate all of these causes before the diagnosis of FUO is reached.

It is important to tell your veterinarian about any recent travel, any potential exposure to unknown or infected animals, any supplements or medications that you are administering or any other information that might be important.

How is FUO treated?

It is important to understand that the diagnostic work-up for FUO may be quite involved. Your veterinarian will search for a specific cause of the fever so that it can be correctly treated and that an accurate prognosis can be given. In cases where a diagnosis is unobtainable, it is reasonable to make a diagnosis of FUO and initiate treatment based on the available information. Antibiotics are often prescribed to treat any underlying bacterial infection or to prevent bacterial infections from occurring as a secondary problem.

“Acetylsalicylic acid (Aspirin®) and acetaminophen (Tylenol®) are extremely toxic to cats and should never be administered by a pet owner without the explicit direction of a veterinarian.”

On rare occasions, medications to reduce the fever will be given. In people, a fever is often treated with a non-steroidal anti-inflammatory drug (NSAID). However, there are only a few, recently developed non-steroidal anti-inflammatory drugs (NSAIDs) that cats can tolerate. Acetylsalicylic acid (Aspirin®) and acetaminophen (Tylenol®) are extremely toxic to cats and should never be administered by a pet owner without the explicit direction of a veterinarian.

What is the prognosis for a cat diagnosed with FUO?

An accurate prognosis can only be given when the cause of a condition is known. By definition, with FUO the exact cause is unknown; therefore, an accurate prognosis cannot be given. Most cats respond well to basic supportive care such as keeping them warm and dry, providing plenty of water and nourishment, and administering antibiotics when indicated. Cats that have persistent fever or a fever that waxes and wanes must undergo a thorough work-up so that the cause of fever can be discovered and treated before irreversible damage occurs. In cases where this pattern repeats more than once, it is imperative that a thorough diagnostic work-up is undertaken.

Fever in Dogs: Causes, Symptoms and Care | Huntersville Veterinary Surgeon

Detecting a fever in dogs can be difficult. Here, our Carolina Veterinary Specialists in Huntersville explains how to detect a fever in dogs, the causes, symptoms, and what you need to know to care for your pet.

What is a normal temperature for a dog and what temperature is a dog fever? 

A dog’s normal body temperature ranges from 101° to 102. 5° Fahrenheit, which is significantly higher than humans whose body temperature ranges from 97.6° to 99.6° F. 

A temperature of more than 103° F is considered a dog fever. When temperatures reach 106° F, serious and fatal complications can occur. 

How can I tell if my dog has a fever and how do I take its temperature? 

It can be difficult to detect fevers in dogs because their body temperatures can also increase when they are very excited or stressed. Also, a dog’s temperature can vary throughout the day and sometimes at night.  Therefore, it is important to understand your dog’s healthy temperature. You can determine this by noting your dog’s temperature at various times of the day, for several days.

Some people believe that if you feel your dog’s nose and if it’s wet and cold your dog’s temperature is fine, and if it is hot and dry it means a fever.  However, this is not an accurate indicator that your dog has a fever.  

The best way to check your dog’s temperature is to use a digital thermometer for rectal use, some pet stores carry thermometers made just for pets.   It is recommended that you keep a separate thermometer just for your dog and store it where you keep your dog’s supplies. 

Start by lubricating the tip of the thermometer with petroleum or water-soluble lubricant. Then lift your dog’s tail up and to the side and carefully insert the thermometer about 1 inch into your dog’s rectum. If possible, have a second person assist you by holding under the dog’s hind legs to prevent your dog from sitting. Once the thermometer temperature has registered you can carefully remove the thermometer.  

Why would a dog have a fever?  

A variety of illnesses and conditions may cause a fever in your dog. These include:

• A bacterial, fungal, or viral infection
• An ear infection
• An infected bite, scratch, or cut 
• Tooth infection or abscess
• Urinary tract infection 
• Ingestion of poisonous materials, such as toxic plants, human medications, or human foods that are toxic to dogs

In some cases, a dog’s fever cannot be readily determined, this is often referred to as a fever of unknown origin or FUO. In these cases, a fever could be caused by underlying disorders of the immune system, bone marrow problems, or cancer.

What are the symptoms of a fever in dogs?  

If you notice a significant change in your dog’s behavior this will be your first sign that your dog is not well. You should keep a careful eye on your dog and take note of your dog’s symptoms. Any combination of the following symptoms is a good indication that you should check your dog’s temperature.  

The most common symptoms of a fever in dogs are: 

• Red or glassy-looking eyes
• Warm ears and/or nose 
• Shivering
• Panting 
• Runny nose 
• Decreased energy 
• Loss of appetite
• Coughing 
• Vomiting

How should I care for a dog with a fever? 

If your dog’s fever is 106° F or higher immediately take your dog to a local veterinary emergency clinic. 

If your dog has a fever, of 103° F or more, you can help to cool your dog’s body temperature by applying cool water with a soaked towel or cloth to your dog’s ears and paws and running a fan near your dog.   Stop applying the water when your dog’s temperature drops below 103° F.  Continue to monitor your dog closely to ensure that the fever doesn’t return.  

Try to coax your dog to drink small amounts of water to stay hydrated, but don’t force your dog to drink. 

It is important to never give your dog human medications, such as acetaminophen or ibuprofen.  These medications can be poisonous to your dog and cause serious injury or death. 

If your dog exhibits any other symptoms, such as shivering, panting, and vomiting you should consider taking your dog to the vet.  

Note: The advice provided in this post is intended for informational purposes and does not constitute medical advice regarding people or pets. Always follow your doctor’s advice regarding asthma or other allergy symptoms. 

Does your dog have a fever? Our Huntersville emergency veterinarians are specially trained in emergency medicine and triage. Any time that you are unable to reach your primary care veterinarian – evenings, weekends, holidays – we are here to help.

 Contact us today.

What will happen if a person’s temperature rises above 43 degrees, – explains the biologist

• Health

There are not even so many divisions on the thermometer – a maximum of 42. So, this is the limit? And will the patient survive with such a fever?

November 23, 2022

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Temperature up to 38 degrees is called subfebrile . It is unpleasant, with an ache, but it does not bother a person much, and they don’t even knock it down, allowing the body to fight the disease.

Another plus degree, up to 39, is febrile temperature. Most often, at this stage, the patient begins to drink an antipyretic in order to prevent a jump to a high or pyretic temperature – 40-41 degrees.

It is dangerous to even think about the fact that it is higher: the temperature is above 41 ^about C – hyperpyretic , that is, excessive. And it is very life-threatening, especially in children.

It seems that the body can no longer be hot. Moreover, divisions are ending on the thermometer. But this is not the limit. And what will happen if the temperature exceeds 43 degrees? Can this even happen and will we survive?

“The speed of our enzymes (biological catalysts for all chemical processes in the body) directly depends on temperature,” Natalya Brik, a biology teacher at the Ellipse online school, explained to our colleagues from the Vokrug Sveta publication. “The highest efficiency lies in the range of 38–40 degrees.”

The expert gives the example of frogs: in cool weather, they move more slowly because their enzyme proteins have lost their activity. When it gets warmer, they are activated, and amphibians again begin to actively jump. This is how metabolism works, and, by the way, it is not easy for animals to maintain a high temperature (and their norm is up to 41 degrees) – a lot of energy is spent on this.

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What about a person? We know about the reference 36.6, but if we start measuring the temperature during the day, it turns out that it is lower in the morning and higher in the evening. These are physiological fluctuations, and the difference can reach a degree: for example, at 6 in the morning the temperature will be exactly 36 degrees, by the evening – 36.9.

“In humans, a temperature above 37 °C is considered abnormal,” says the biologist. “A body temperature above 40 ° C is dangerous, because protein enzymes are destroyed, there is a lack of oxygen, the temperature sensor-regulator in the brain goes astray, consciousness turns off.”

At the same time, many deliberately try not to bring down the temperature, even when it is already over the top, believing that this way the body will quickly overcome the disease. But you need to understand that an indicator of 42 degrees is considered critical, and 43 is fatal.

“There are rare cases of fortunate people who were able to survive even higher temperatures, such as sunstroke. But for most people, 40 ° C on a thermometer is already very dangerous, ”concludes Natalya Brik.

Text author:Irina Sebeleva

Body temperature in an elderly person – the norm and tolerances

Body temperature is one of the most informative indicators by which one can judge the state of the body. The ideal parameter is considered to be the mark of 36.6 on the thermometer, however, in the elderly and senile age, body temperature does not always correspond to the generally accepted norm. Reduced immunity, exacerbation of chronic diseases, the extinction of natural protective functions – the body of a pensioner lives according to its own “laws”. To determine what temperature an elderly person should have, you need to take into account many factors and take into account individual characteristics.

Normal temperature is a sign of good health

It is important to remember that a person’s temperature changes over 24 hours. Measurements are affected by factors such as time of day, environment, and even mood. It is necessary to measure the temperature at the same time for several days, it is desirable that the state of health at these moments be satisfactory.

Record the results in a notebook. After 3-5 days, you can analyze the indicators and calculate the average value – this will be the norm.

No need to be scared if the thermometer shows numbers above or below the usual 36.6 ° C. A slightly increased or decreased body temperature in an elderly person is an acceptable deviation. The range from 35.8°C to 36.9°C is considered to be the normal range. Anything that goes beyond these limits should be alarming: this is a reason to immediately consult a doctor.

Hyperthermia: causes, symptoms

If the body temperature has risen by 1-1.5 degrees or more, there is hyperthermia of the body, which is one of the signs of an inflammatory process, injury or viral infection. To say exactly what the diagnosis is at a high temperature in the elderly, only a doctor can after all the necessary tests and examinations. It is important to consider other accompanying symptoms.

If hyperthermia is accompanied by high blood pressure, we can talk about a panic attack, a heart attack, an impending heart attack, kidney failure, or hormonal failure. In cases where fever is accompanied by weakness, runny nose, sore throat, it can be SARS, flu or tonsillitis.

It is much more difficult to make a diagnosis if a pensioner with hyperthermia has no other complaints. A thorough examination is required, since such a situation may be a manifestation of one of the following diseases:

• malignant neoplasm;
• tuberculosis;
• diseases of the thyroid gland;
• inflammation of tissues and joints;
• intestinal infection.

An increase in temperature without accompanying symptoms means that the body is struggling with some kind of hidden disease. To identify the cause, you need to take tests of urine, blood, bile. By the way, it is not recommended to bring down the temperature immediately. Only if the indicators reach 38-38.5 ° C, you can give an antipyretic. Until then, the body itself must try to fight the infection. Wet compresses on the forehead, regular heavy drinking will help to ease the patient’s well-being. Wiping with vodka or diluted alcohol has a good effect. After wiping, you do not need to cover the patient with a blanket: the skin should breathe and cool.

Hypothermia: features of the condition

A low body temperature in an elderly person is called hypothermia. The most common reason is hypothermia: against the background of slow biological processes occurring in the body, a pensioner does not always immediately notice that he is very cold (signals to the brain in old age come more slowly). The consequence of hypothermia can be a cold, so when going for a walk, it is important to carefully consider all the details of the wardrobe, do not forget to wear a hat, gloves, scarf in the cold season.

However, a low temperature in an elderly man or woman can be caused by other reasons (especially if we are talking not about the short-term, but about the chronic nature of the deviations):

• previous chemotherapy;
• renal insufficiency;
• disorders of the central nervous system;
• diabetes mellitus.

Sometimes relatives do not even realize that the cause of weakness and loss of strength is a low body temperature. You need to get a thermometer with the following symptoms:

• frequent dizziness, drowsiness;
• numbness of limbs;
• decreased reactions;
• pallor or cyanosis of the skin;
• violation of concentration.

In private boarding houses, for example, the daily measurement of body temperature in guests is a common practice. This allows you to constantly monitor the condition of the elderly and take immediate action at the slightest ailment.

Stages of hypothermia

Doctors distinguish several stages of hyperthermia. For example, many are interested in why an elderly person has a temperature of 35.5, what does this mean? It turns out that fluctuations in the thermometer readings within 1-1.5 degrees below the norm are acceptable, not critical deviations. If, in a normal state, a pensioner is below 35 ° C, this can no longer be ignored, some hidden processes are taking place in the body.

If there is a chill in an elderly person without a temperature, this is a borderline condition, we are talking about a serious threat to life. An indicator of 32 ° C is defined as a severe degree.

Therefore, three stages of hypothermia can be distinguished:

1. Light . The body temperature of an elderly person drops to 34°C. The patient develops chills, the skin turns pale, the nasolabial fold becomes bluish. The pressure is normal, the patient moves independently.
2. Medium . Body temperature drops to 32°C. A person has weakness, apathy, indifference to everything that happens. The patient practically does not react to external stimuli. Cannot move without assistance.
3. Heavy . The temperature drops below 32-31°C. This stage is accompanied by a slow pulse (30-35 beats per minute), rare, weak breathing. The patient may lose consciousness and fall into a coma.

You need to know how to provide first aid for a decrease in body temperature and hypothermia.

First aid for hypothermia

It is important to remember that representatives of the older generation do not perceive temperature fluctuations well. Any deviation from the norm entails circulatory disorders, metabolic deterioration, malfunctions of the central nervous system. With hypothermia, you can not self-medicate: the body can react unpredictably to certain drugs. You need to see a doctor, and before the visit of a specialist, take care of the patient as follows:

• put on warm socks, cover with a blanket;
• prepare a hot drink: compote, broth, tea;
• close doors and windows to keep the room at a comfortable temperature;
• make a light massage of the hands and feet.

These measures will help to cope with a short-term decrease in body temperature, but if we are talking about a chronic condition, drug therapy is indispensable.

Hypothermia can also indicate severe frostbite, a life-threatening condition. In this case, drinking plenty of water and warm clothes will not help, you need to urgently call an ambulance. Doctors will treat the wound surfaces, remove dead skin areas, and prescribe painkillers without fail. Due to the high risk of infection of the body, antibiotics are usually prescribed. The healing process will be accelerated by special ointments and creams with which the patient will have to treat the affected areas.

How body temperature and medication are related

If an elderly person is prescribed medications, it is also important to arm yourself with a thermometer while taking them. Some medications cause causeless changes in body temperature, which adversely affect the general condition of the pensioner.

This side effect often occurs after taking the following remedies:

• antibiotics;
• anti-inflammatory agents;
• antihistamine tablets and mixtures;
• iodine;
• preparations for the treatment of blood vessels and heart diseases.

This phenomenon is usually short-term and disappears after the end of the course of treatment.

Prevention of changes in body temperature in the elderly

In order for the body temperature to be constantly within the normal range in the elderly and senile age, experts recommend prophylaxis, which consists of simple, uncomplicated rules:

• Harden, strengthen immunity with the help of vitamins.
• Review the diet, refuse fried, spicy, smoked delicacies. Give preference to lean meat, boiled fish, fruits, vegetables, nuts, greens.
• Ventilate the home twice a day, in any weather, for at least a few minutes.
• Provide the body with gentle physical activity (walking in the fresh air, climbing stairs, doing morning exercises).
• Dress according to the weather, choose clothes made from natural materials.

Experts agree that sudden changes in body temperature with a relatively normal state of health in older people are observed in an unfavorable psychological situation in the family.