- Histoplasma capsulatum var. farciminosum
- Similar to H. capsulatum
- Occurs in horses, donkeys and mules
- 90% occurs in horses
- Occurs in Europe, Africa and Asia
- Eradicated from the UK but is still under the notifiable Diseases of Animals Act
- Chronic disease
- Highly contageous
- Spread by direct contact or indirect, e.g. through infected grooming equipment, biting flies
- Once established in a population it is very difficult to eradicate
- Long incubation peroid
- New cases can develop weeks or months after the infection appears to have been eradicated
- Affects the lymph nodes, lymph vessels and skin
- Mostly of the neck and limbs
- Causes ulcerative, nodular lesions
- Dissemination occurs
- Pulmonary disease can occur
- Ulcers rupture, discharging blood-stained pus for several weeks
- Oval or pear shaped cells
- Double contoured
- Dimorphic
- Grows in the yeast phase at 37°C and in the mycelial phase at room temperature
- Growth is slow, taking up to 8 weeks
- At room temperature, thick-walled chlamydospores can be seen
- Orgnaisms can usually be seen in swollen leucocytes
- Can be stained using Gram, Giemsa, H & E and 10% Methylene Blue followed by Carbol Fuchsin
- Enzyme-linked immunosorbant assay can be used to detect the fungi
- Life-long immunity follows recovery from infection
- Treatment included potassium iodide, hamycin and Amphotericin B
- Vaccination has also proven to be effective
- Injection of hyperimmune serum around skin lesions has been proven to be effective