Conidiobolus

Conidiobolus species are members of the Phylum Glomeromycota. These fungi are often found in decaying plant matter and soil, and can also exist as insect pathogens. Conidiobolus infections occur worldwide, predominantly in tropical and subtropical climates. Several species of Conidiobolus have been reported to cause disease in both humans and animals. These species include C. coronatus, C. incongruus, and C. lamprauges. C. coronatus is a well-known pathogen of horses and humans, especially in the tropics. It also causes infections in chimpanzees. C. incongruus causes rhinocerebral and and nasal zygomycosis in sheep. C. lamprauges has been isolated from a nasopharyngeal nodule of a horse.2

Conidiobolus growing in petri dish
Source: Med Mycol Case Rep. 2015 June

Conidiobolomycosis is usually a localized infection that is most commonly caused by C. coronatus. Clinically, the infection manifests as a nasopharyngeal disease that can extend to include the tissues of the face, retropharyngeal region, and regional lymph nodes. Patients may have chronic nasal disease, nodular subcutaneous lesions, ulcerative dermatitis or, less commonly, pneumonia.1 In horses, most lesions are found on the external nares or nasal passages. Within the passages there are usually coalescing firm nodules with either a cobblestone appearance or ulceration.3

Conidiobolomycosis usually progresses over many years and is frequently fatal in immunocompromised patients. However, unlike the protracted clinical course typical of most cases of zygomycosis, nasal zygomycosis in sheep caused by C. incongruus results in loss of condition and death within 7-10 days after initial clinical signs. This infection produces prominent swelling of the face, extending from the nostrils to the eyes, and marked thickening of the skin and subcutaneous tissue.

Although C. coronatus is susceptible to amphotericin B, and although iodides, ketoconazole, floconazole, or surgery have resulted in instances of improvement in some people, there is no consistently effective treatment for conidiobolomycosis.2

References

  1. Disseminated Conidiobolus incongruus in a dog: A case report and literature review
  2. Pathogenic Fungi in Humans and Animals. D.H. Howard
  3. Jubb, Kennedy & Palmer's Pathology of Domestic Animals: 3-Volume Set. Grant Maxie

 

 

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