# Histoplasmosis in Dogs: Signs, Causes, and Treatment Options \(Vet Answer\) - Canonical: https://33rdsquare.com/histoplasmosis-in-dogs-signs-causes-and-treatment-options/ - Published: 2024-02-02 - Author: Savanna Read - Categories: [Dog](https://33rdsquare.com/category/dog/) --- Histoplasmosis in Dogs: Causes, Symptoms, and Treatment Options As a dog lover and veterinarian, one of the more concerning fungal diseases I see in my canine patients is histoplasmosis. This soil-borne infection, caused by the Histoplasma capsulatum fungus, can lead to serious and sometimes life-threatening illness in dogs. While histoplasmosis is treatable, it requires prompt veterinary care and diligent anti-fungal therapy to achieve the best outcome. In this article, we‘ll take an in-depth look at histoplasmosis in dogs, including how dogs contract this fungal infection, the signs to watch for, diagnostic and treatment options, and ways to reduce your dog‘s risk of exposure. As a vet, I hope this information will help you protect your pup from this hidden soil fungus and know what to do if your dog does develop histoplasmosis. What is Canine Histoplasmosis? Histoplasmosis is a fungal infection caused by the soil-dwelling fungus Histoplasma capsulatum. This microscopic fungus thrives in moist, organic-rich soil, especially soil that has been contaminated with bird or bat droppings. When the soil is disturbed, fungal spores become airborne and can be inhaled into a dog‘s lungs or enter the gastrointestinal tract if ingested. In the United States, Histoplasma is most prevalent in the central and eastern states along the Mississippi, Missouri, and Ohio River valleys. However, this fungus has a worldwide distribution and can be found in parts of Central and South America, Africa, Asia and Australia as well. Histoplasmosis affects both humans and animals, with dogs and cats being the most commonly infected pet species. Once inside a dog‘s body, the inhaled or ingested Histoplasma spores settle in the lungs, intestines or other organs and transform into yeast. The fungal yeast cells then replicate and spread, causing inflammation and granulomas (areas of inflamed tissue) to form. If the immune system doesn‘t quickly wall off the infection, it can spread systemically through the bloodstream and lymphatic system to affect multiple parts of the body. Which Dogs Are At Risk for Histoplasmosis? Any dog exposed to Histoplasma spores in the environment can potentially develop histoplasmosis. However, some dogs seem to be at higher risk of contracting this fungal infection, including: - Young dogs under 4 years old with immature immune systems - Hunting dogs and other breeds that spend a lot of time outdoors in wooded areas - Dogs living near farms, old barns, chicken coops, caves, or other areas with large bird or bat populations - Immunocompromised dogs with weakened immune systems due to underlying illness, malnutrition, or immunosuppressive medications Studies have found that sporting breeds like pointers, Weimaraners and Brittany spaniels have higher rates of histoplasmosis, likely due to their increased environmental exposure from hunting and field activities. However, histoplasmosis can affect any breed. Signs and Symptoms of Histoplasmosis in Dogs Histoplasmosis signs in dogs are often vague and nonspecific, especially in early or mild infections. Some infected dogs may show no outward signs at all while others can become extremely ill. After inhaling or ingesting fungal spores, it typically takes 2-4 weeks before symptoms start to appear. The severity of signs depends on the fungal dose and the dog‘s immune response. Potential signs of histoplasmosis in dogs include: - Fever - Lethargy and weakness - Decreased appetite and weight loss - Chronic cough - Difficulty breathing or rapid breathing - Eye inflammation (uveitis) - Enlarged lymph nodes - Diarrhea, which may contain blood or mucus - Vomiting - Pale gums due to anemia - Liver or spleen enlargement - Lameness or joint pain - Skin lesions or nodules that may ulcerate and drain If the infection spreads systemically, affecting multiple organ systems, dogs can develop severe debilitating illness. Ocular histoplasmosis can quickly lead to glaucoma, retinal detachment and blindness if untreated. The fungal infection can also cause meningitis if it reaches the central nervous system. Untreated disseminated histoplasmosis will eventually lead to death. Diagnosing Histoplasmosis in Dogs Recognizing and diagnosing histoplasmosis in dogs can be tricky due to the nonspecific signs. Veterinarians will first take a thorough history to determine if your dog may have been exposed to the Histoplasma fungus through environmental exposure or travel to an endemic region. Your vet will then perform a full physical exam to check for fever, enlarged lymph nodes, respiratory symptoms, eye inflammation, and other indicators of histoplasmosis. If histoplasmosis is suspected, your vet will likely recommend some diagnostic tests, which may include: - Complete blood count to check for anemia, low platelet count, and high white blood cell levels - Blood chemistry panel to evaluate kidney and liver function - Urinalysis to look for blood, protein, or Signs of kidney disease - Chest x-rays to visualize lung changes and check for pneumonia - Abdominal x-rays or ultrasound to assess the liver, spleen, intestines and lymph nodes - Lymph node, bone marrow, or organ aspirates to identify Histoplasma yeast under the microscope - Histoplasma urine or blood antigen tests - PCR (polymerase chain reaction) to detect fungal DNA in blood or tissue samples - Serologic antibody titer tests A definitive diagnosis of histoplasmosis requires finding the characteristic Histoplasma yeast on microscopic examination of tissue samples or via culture. However, blood and urine antigen tests have become useful, rapid screening tools that can detect early infections before the fungus is apparent microscopically. Treating Histoplasmosis in Dogs Histoplasmosis is a serious systemic fungal infection, but fortunately it can be treated using oral anti-fungal medications. The treatment of choice for canine histoplasmosis is itraconazole, a triazole antifungal drug that is highly effective against Histoplasma. Compounded itraconazole liquids are preferable over capsules for more accurate dosing. The main drawback of itraconazole is that it must be given daily by mouth for an extended period, typically a minimum of 4-6 months, to fully clear the fungal infection. Some dogs may require treatment for a year or longer. During treatment, it‘s important to monitor liver enzymes and itraconazole blood levels to check for toxicity and ensure therapeutic levels are reached. Fluconazole is sometimes used as an alternative if a dog can‘t tolerate itraconazole, but it‘s not quite as effective. Amphotericin B is another option reserved for severe, life-threatening cases of disseminated histoplasmosis. In addition to antifungal therapy, dogs with moderate to severe histoplasmosis may require supportive treatments like: - IV fluids - Anti-inflammatories - Pain relief - Antibiotics for secondary bacterial infections - Oxygen therapy - Nutritional support - Eye medications Dogs typically start to improve within the first 1-2 weeks of treatment. However, complete recovery is a long process and frequent recheck exams and lab work are needed to monitor treatment response over the following months to year. Histoplasmosis Prognosis and Prevention The prognosis for dogs with histoplasmosis is generally good if the infection is diagnosed early and treated appropriately with a long course of antifungal medication. Most dogs that aren‘t severely debilitated have a 70-80% survival rate with treatment. However, dogs that develop disseminated systemic infections affecting multiple organs have a more guarded prognosis, especially if their bone marrow is affected. Ocular histoplasmosis can also be more challenging to eradicate and may result in permanent vision deficits even if the infection is cleared. Relapses can sometimes occur, so it‘s important to give the full duration of antifungal medication and follow up with your vet as advised. Dogs with impaired immunity may need to stay on a low preventative dose of itraconazole long-term if they remain in an endemic environment. There‘s no vaccine for histoplasmosis in dogs. The best way to prevent the disease is to limit your dog‘s exposure to areas where Histoplasma is likely to be present in the soil, such as: - Chicken coops and poultry houses - Parks frequented by birds or bats - Caves - Areas around old barns or decaying wood Keep your dog from digging or sniffing in soil, especially if it contains bird or bat droppings. Supervise your dog outdoors and consider using a basket muzzle if they tend to eat soil or animal feces. Histoplasmosis is uncommon in humans but people can be infected by inhaling fungal spores from contaminated soil. Having an infected pet doesn‘t pose a significant transmission risk but it‘s still a good idea to practice good hygiene, like wearing gloves and washing your hands, when cleaning up after your dog. Avoid letting your dog lick your face and keep them out of the bedroom. If you live in an endemic region and your dog develops a chronic cough, fever, eye inflammation, diarrhea, or enlarged lymph nodes, have your vet check them promptly for histoplasmosis. Starting antifungal treatment as early as possible will give your dog the best chance at a full recovery. --- Source: [Histoplasmosis in Dogs: Signs, Causes, and Treatment Options \(Vet Answer\)](https://33rdsquare.com/histoplasmosis-in-dogs-signs-causes-and-treatment-options/)