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Cryptococcosis in dogs
What is Cryptococcosis?
Cryptococcosis is a disease caused by a fungus named Cryptococcus neoformans. This disease is much more common in cats, but dogs and humans do get it occasionally. When a dog becomes in infected with Cryptococcus neoformans, it can cause severe damage by spreading to the central nervous system. Humans rarely get Cryptococcosis unless they have a compromised immune system, e.g. due to immune repressing drugs taken after transplants.
Cryptococcosis transmission to dogs
Cryptococcus neoformans is found all over the world and various environments. It is commonly found in soil and bird droppings, especially pigeon droppings, which make it widespread in spots where wild or domesticated pigeons occur in large number. Transmission to dogs usually occurs via inhalation of spores, but the spores can also enter through damaged skin. When Cryptococcus neoformans occurs in bird droppings, it can be in its non-capsulated form. This form is no bigger than 1 µmand can therefore be inhaled into the deeper parts of the dog's lungs.
Cryptococcosis symptoms in dogs
Compared to cats, dogs are more prone to develop the disseminated for of the disease. Disseminated Cryptococcosis means that the fungi have spread from the original point of entry to other parts of the dog's body. Cryptococcus neoformans can affect the eyes and the central nervous system (CNS) and cause optic neuritis, granulomatous chorioretinitis and meningoencephalitis. Roughly 50 percent of the diagnosed dogs have lesions in their respiratory tract, most commonly the lungs, and most dogs have granulomas in more than one system. Lesions can develop in the nasal cavity. Cryptococcus neoformans quite frequently attack the kidneys, lymph nodes, spleen and liver of the dog, and less commonly the tonsils, heart valves, thyroid, adrenals, muscles, pancreas, GI tract, bones, myocardium, and the prostate.
When Cryptococcosis causes lesions in dogs, they can vary from granulomas to a sort of gelatinous mass made up by numerous organisms (often with very little inflammation). Cryptococcosis lesions in dogs usually consist of aggregates of encapsulated organisms protected by a connective tissue reticulum.
Cryptococcosis treatment for dogs
In most situations, the preferred Cryptococcosis treatment for a dog is Fluconazole or Itraconazole. The normal Fluconazole dose for dogs suffering from Cryptococcosis varies from 2 to 10 mg of Fluconazole per kilogram bodyweight per day. When Itraconazole is used, the standard dose is 10 mg per per kilogram bodyweight per day. Another possibility is Flucytosine, but drug resistance can develop if your dog gets only Flucytosine and most veterinarians therefore chose to combine it with Amphotericin B.
Subcutaneously administered Amphotericin B is commonly used for severe Cryptococcosis infections in dogs, normally 0.5-0.8 mg/kg diluted in 0.45% saline containing 2.5% dextrose. If the dog weighs up to 20 kg, 500 millilitres is enough. If the dog weighs over 20kg, 1,000 millilitres is the standard dose. Subcutaneously administered Amphotericin B is normally administered 2-3 times per day for dogs suffering from severe Cryptococcosis. Amphotericin B lipid complex is another alternative here; the standard dose for dogs with Cryptococcosis is 2-3 mg/kg, administered 3 times per week. The treatment regiment normally has to include at least 12-15 treatments, i.e. go on for at least 4 to 5 weeks.
West Highland White Terrier