Phycomycosis

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Phycomycosis
Causesvarious species of fungi and oomycota

Phycomycosis is an uncommon condition affecting the gastrointestinal tract and skin, most commonly found in dogs and horses. The condition is caused by various molds (a type of fungi), with individual forms including pythiosis, zygomycosis, and lagenidiosis. Pythiosis, the most common type, is caused by Pythium , a type of water mould. Zygomycosis can be caused by two types of zygomycetes: Entomophthorales (e.g., Basidiobolus and Conidiobolus ) and Mucorales (e.g., Mucor , Mortierella , Absidia , Rhizopus , Rhizomucor , and Saksenaea ). [1] The latter type of zygomycosis is also referred to as mucormycosis. Lagenidiosis is caused by a Lagenidium species, which like Pythium is a water mould. Since both pythiosis and lagenidiosis are caused by organisms from the Oomycetes and not the kingdom fungi, they are sometimes collectively referred to as oomycosis.

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Pythiosis

Ulcerative and destructive skin lesion on a dog caused by Pythium insidiosum Pythiosis 2.jpg
Ulcerative and destructive skin lesion on a dog caused by Pythium insidiosum

Pythiosis is caused by Pythium insidiosum and occurs most commonly in dogs and horses, but is also found in cats, cattle, and humans. In the United States, it is most commonly found in states bordering the Gulf of Mexico , especially Louisiana, but has been found in the Midwest and Eastern states. It is also found in Southeast Asia, eastern Australia, New Zealand, and South America. Pythiosis occurs in areas with mild winters due to the organism surviving in standing water that does not reach freezing temperatures. [2] Pythium occupies swamps in late summer and infects dogs who drink water containing it. The disease is typically found in young, large breed dogs. [1]

It is suspected that pythiosis is caused by invasion of the organism into wounds, either in the skin or in the gastrointestinal tract. [2] The disease grows slowly in the stomach and small intestine, eventually forming large lumps of granulation tissue. It can also invade surrounding lymph nodes. Symptoms include vomiting, diarrhea, weight loss, a mass in the abdomen, and depression. Pythiosis of the skin in dogs is very rare, and appears as ulcerated lumps. Primary infection can also occur in the bones and lungs.

Pythium hyphae Pythiosis hyphae.jpg
Pythium hyphae

In horses, subcutaneous pythiosis is the most common form and infection occurs through a wound while standing in water containing the pathogen. [3] The disease is also known as leeches, swamp cancer, and bursatti. Lesions are most commonly found on the lower limbs, abdomen, chest, and genitals. They are granulomatous and itchy, and may be ulcerated or fistulated. The lesions often contain yellow, firm masses of dead tissue known as kunkers. [4] It is possible with chronic infection, the disease can spread to underlying bone. [5]

In cats, pythioisis is almost always confined to the skin as hairless and edematous lesions. It is usually found on the limbs, perineum, and at the base of the tail. [6] Lesions may also develop in the nasopharynx. [4]

In humans, it can cause arteritis, keratitis, and periorbital cellulitis. [7]

Pythium insidiosum is different from other members of the genus in that human and horse hair, skin, and decaying animal tissue are chemoattractants for its zoospores, in addition to decaying plant tissue. [3]

Zygomycosis

A mature sporangium of a Mucor sp. fungus Mature sporangium of a Mucor sp. fungus.jpg
A mature sporangium of a Mucor sp. fungus

Usually, zygomycosis is a disease of the skin, but can also occur in the sinuses or gastrointestinal tract. In humans, it is most prevalent in immunocompromised patients (human immunodeficiency virus/acquired immunodeficiency syndrome [ HIV/AIDS], the elderly, severe combined immunodeficiency [ SCID], etc.) and patients with acidosis (i.e., diabetes, burns), particularly after barrier injury to the skin or mucous membranes. Zygomycosis caused by Mucorales causes a rapidly progressing disease of sudden onset in sick or immunocompromised animals. Entomophthorales cause chronic, local infections in otherwise healthy animals. The important species that causes entomophthoromycosis are Conidiobolus coronatus, C. incongruous, and Basidiobolus ranarum . Conidiobolus infections of the upper respiratory system have been reported in humans, sheep, horses, and dogs, and Basidiobolus has been reported less commonly in humans and dogs. [8] Horses are one of the most common domestic animals to be affected by entomophthoromycosis. C. coronatus causes lesions in the nasal and oral mucosa of horses that may cause nasal discharge or difficulty breathing. B. ranarum causes large circular nodules on the upper body and neck of horses. [9] Entomophthorales is found in soil and decaying plant matter, and specifically, Basidiobolus can be contracted from insects and the feces of reptiles or amphibians. [7]

Zygomycosis of the sinuses can extend from the sinuses into the orbit and the cranial vault, leading to rhinocerebral mucormycosis.[ citation needed ]

Lagenidiosis

The best known species of Lagenidium is Lagenidium giganteum , a parasite of mosquito larvae used in the biological control of mosquitoes. Two different species cause disease exclusively in dogs: L. caninum and L. karlingii. Lagenidium is found in the Southeastern United States in lakes and ponds. Lagenidiosis causes progressive skin and subcutaneous lesions in the legs, groin, trunk, and near the tail. The lesions are firm nodules or ulcerated regions with draining tracts. Regional lymph nodes are usually swollen. Spread of the disease to distant lymph nodes, large blood vessels, and the lungs may occur. [7] An aneurysm of a great vessel can rupture and cause sudden death. [4] L. caninum is the more aggressive species and is more likely to spread to other organs than L. karlingii. [10]

Diagnosis and treatment

Diagnosis is through biopsy or culture, although an enzyme-linked immunosorbent assay (ELISA) test has been developed for Pythium insidiosum in animals. [11] Treatment is very difficult and includes surgery when possible. Postoperative recurrence is common. Antifungal drugs show only limited effect on the disease, but itraconazole and terbinafine hydrochloride are often used for 2 to 3 months following surgery. [7] Humans with Basidiobolus infections have been treated with amphotericin B and potassium iodide. [8] For pythiosis and lagenidiosis, a new drug targeting water moulds called caspofungin is available, but it is very expensive. [7] Immunotherapy has been used successfully in humans and horses with pythiosis. [11] The prognosis for any type of phycomycosis is poor.

Related Research Articles

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<span class="mw-page-title-main">Zygomycosis</span> Medical condition

Zygomycosis is the broadest term to refer to infections caused by bread mold fungi of the zygomycota phylum. However, because zygomycota has been identified as polyphyletic, and is not included in modern fungal classification systems, the diseases that zygomycosis can refer to are better called by their specific names: mucormycosis, phycomycosis and basidiobolomycosis. These rare yet serious and potentially life-threatening fungal infections usually affect the face or oropharyngeal cavity. Zygomycosis type infections are most often caused by common fungi found in soil and decaying vegetation. While most individuals are exposed to the fungi on a regular basis, those with immune disorders (immunocompromised) are more prone to fungal infection. These types of infections are also common after natural disasters, such as tornadoes or earthquakes, where people have open wounds that have become filled with soil or vegetative matter.

Skin disorders are among the most common health problems in dogs, and have many causes. The condition of a dog's skin and coat is also an important indicator of its general health. Skin disorders of dogs vary from acute, self-limiting problems to chronic or long-lasting problems requiring life-time treatment. Skin disorders may be primary or secondary in nature, making diagnosis complicated.

<span class="mw-page-title-main">Mastocytoma</span> Medical condition

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<span class="mw-page-title-main">Pythiosis</span> Tropical disease caused by the oomycete Pythium insidiosum

Pythiosis is a rare and deadly tropical disease caused by the oomycete Pythium insidiosum. Long regarded as being caused by a fungus, the causative agent was not discovered until 1987. It occurs most commonly in horses, dogs, and humans, with isolated cases in other large mammals. The disease is contracted after exposure to stagnant fresh water such as swamps, ponds, lakes, and rice paddies. P. insidiosum is different from other members of the genus in that human and horse hair, skin, and decaying animal and plant tissue are chemoattractants for its zoospores. Additionally, it is the only member in the genus known to infect mammals, while other members are pathogenic to plants and are responsible for some well-known plant diseases.

Hypertrophic osteopathy is a bone disease secondary to cancer in the lungs.

<span class="mw-page-title-main">Corneal ulcers in animals</span> Veterinary inflammatory condition of the cornea

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Lagenidiosis is a type of infectious disease caused by a species of Lagenidium that has not yet been properly named. Lagenidiosis is found in the southeastern United States in lakes and ponds. It causes progressive skin and subcutaneous lesions in the legs, groin, trunk, and near the tail. The lesions are firm nodules or ulcerated regions with draining tracts. Regional lymph nodes are usually swollen. Spread of the disease to distant lymph nodes, large blood vessels, and the lungs may occur. Invasion and subsequent aneurysm of a great vessel can cause death.

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<span class="mw-page-title-main">Basidiobolomycosis</span> Fungal disease

Basidiobolomycosis is a fungal disease caused by Basidiobolus ranarum. It may appear as one or more painless firm nodules in the skin which becomes purplish with an edge that appears to be slowly growing outwards. A serious but less common type affects the stomach and intestine, which usually presents with abdominal pain, fever and a mass.

<i>Basidiobolus ranarum</i> Species of fungus

Basidiobolus ranarum is a filamentous fungus with worldwide distribution. The fungus was first isolated by Eidam in 1886. It can saprophytically live in the intestines of mainly cold-blooded vertebrates and on decaying fruits and soil. The fungus prefers glucose as a carbon source and grows rapidly at room temperature. Basidiobolus ranarum is also known as a cause of subcutaneous zygomycosis, usually causing granulomatous infections on a host's limbs. Infections are generally geographically limited to tropical and subtropical regions such as East and West Africa. Subcutaneous zygomycosis caused by B. ranarum is a rare disease and predominantly affects children and males. Common subcutaneous zygomycosis shows characteristic features and is relatively easy to be diagnosed; while, certain rare cases might show non-specific clinical features that might pose a difficulty on its identification. Although disease caused by this fungus is known to resolve spontaneously on its own, there are a number of treatments available.

Entomophthoramycosis is a mycosis caused by Entomophthorales.

<i>Pythium insidiosum</i> Species of single-celled organism

Pythium insidiosum is a species of Pythium and a member of the class oomycota. Pythium insidiosum is mainly found in standing water and occasionally soil. Unlike most Pythium species, which are generally pathogens of terrestrial plants, Pythium insidiosum is a pathogen of mammals. It causes pythiosis, mainly in horses, dogs, and humans. It can also cause disease in cats. It is a non-transmissible disease and occurs mainly in tropical climate, endemic to Thailand, affecting mainly humans and horses and in Brazil, affecting mainly horses. Infection can occur in healthy mammals. The pathogen is well-adapted to mammalian body temperature, with an optimum temperature for growth of 34–36 °C (93–97 °F).

Phaeohyphomycosis is a diverse group of fungal infections, caused by dematiaceous fungi whose morphologic characteristics in tissue include hyphae, yeast-like cells, or a combination of these. It can be associated with an array of melanistic filamentous fungi including Alternaria species, Exophiala jeanselmei, and Rhinocladiella mackenziei.

Autoimmune skin diseases occur when the immune system of an infected animal attacks its own skin. In dogs, autoimmune skin diseases are usually not detected until visible symptoms appear, which differs from detection in humans who are able to verbally express their concerns. Genetics, nutrition, and external environmental factors all collectively contribute to increasing the probability an autoimmune skin disease occurring. The severity of symptoms varies based on the specific disease present and how far it has progressed. Diagnosis often requires the onset of visible symptoms and for a biopsy to be performed. For many diseases, the condition itself cannot be cured, but a veterinarian can prescribe medications and other forms of treatment to help manage the symptoms of the dog.

<i>Lagenidium giganteum forma caninum</i> Species of single-celled organism

Lagenidium giganteum forma caninum is a fungus-like organism belonging to the genus Lagenidium and causes lagenidiosis in some mammal species. Lagenidiosis is a disease characterized by progressive, severe and invasive cutaneous, subcutaneous and disseminated infection. Clinical and pathological aspects of the disease are almost identical to pythiosis. The first cases of lagenidiosis in mammals were officially reported in dogs in 2003. Since then, it has become increasingly recognized in dogs and cats as a cause of skin lesions.

Basidiobolus haptosporus belongs to the Kingdom Fungi and is a member of a grouping known as the "zygomycetes". This classification comprises two Phyla- the Mucoromycota and the Zoopagomycota, which are characterized by the production of sexual zygospores and suspensor cells. B. haptosporus is a filamentous fungus with distribution concentrated in Tropical and Subtropical regions. This fungus is largely associated with the gastrointestinal tract of amphibians and reptiles but has also been reported on mite bristles. B. haptosporus has caused disease in humans as well, including Gastrointestinal entomophthoromycosis and subcutaneous phycomycosis. Closely related species include Basidiobolus ranarum, B. meristosporus, B. microsporus, and B. magnus.

References

  1. 1 2 Ettinger, Stephen J.; Feldman, Edward C. (1995). Textbook of Veterinary Internal Medicine (4th ed.). W.B. Saunders Company. ISBN   0-7216-6795-3.
  2. 1 2 Helman R, Oliver J (1999). "Pythiosis of the digestive tract in dogs from Oklahoma". J Am Anim Hosp Assoc. 35 (2): 111–4. doi:10.5326/15473317-35-2-111. PMID   10102178.
  3. 1 2 Liljebjelke K, Abramson C, Brockus C, Greene C (2002). "Duodenal obstruction caused by infection with Pythium insidiosum in a 12-week-old puppy". J Am Vet Med Assoc. 220 (8): 1188–91, 1162. doi: 10.2460/javma.2002.220.1188 . PMID   11990966.
  4. 1 2 3 "Oomycosis". The Merck Veterinary Manual. 2006. Retrieved 2007-02-03.
  5. ↑ Worster A, Lillich J, Cox J, Rush B (2000). "Pythiosis with bone lesions in a pregnant mare". J Am Vet Med Assoc. 216 (11): 1795–8, 1760. doi: 10.2460/javma.2000.216.1795 . PMID   10844973.
  6. ↑ Wolf, Alice (2005). "Opportunistic fungal infections". In August, John R. (ed.). Consultations in Feline Internal Medicine Vol. 5. Elsevier Saunders. ISBN   0-7216-0423-4.
  7. 1 2 3 4 5 Grooters A (2003). "Pythiosis, lagenidiosis, and zygomycosis in small animals". Vet Clin North Am Small Anim Pract. 33 (4): 695–720, v. doi:10.1016/S0195-5616(03)00034-2. PMID   12910739.
  8. 1 2 Greene C, Brockus C, Currin M, Jones C (2002). "Infection with Basidiobolus ranarum in two dogs". J Am Vet Med Assoc. 221 (4): 528–32, 500. doi: 10.2460/javma.2002.221.528 . PMID   12184703.
  9. ↑ "Zygomycosis". The Merck Veterinary Manual. 2006. Retrieved 2007-02-03.
  10. ↑ Todd-Jenkins, Karen (September 2007). "A new disease: clinically interesting for all the right reasons". Veterinary Forum. 24 (9). Veterinary Learning Systems: 18–20.
  11. 1 2 Hensel P, Greene C, Medleau L, Latimer K, Mendoza L (2003). "Immunotherapy for treatment of multicentric cutaneous pythiosis in a dog". J Am Vet Med Assoc. 223 (2): 215–8, 197. doi:10.2460/javma.2003.223.215. PMID   12875449.
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