One Health: Fungal pathogens of Humans & Animals

 

One Health: Fungal pathogens of Humans & Animals

Prateek Jindal¹ and Kriti Singh²

¹Assistant Professor, KVK, Barnala

²Ph.D. Scholar, Centre for One Health

Guru Angad Dev Veterinary & Animal Sciences University, Ludhiana 141004 (Punjab)

 HISTOPLASMOSIS (Reticuloendothelial cytomycosis/ Cavern disease/ Darling’s disease)

Chronic, non-contagious, disseminated granulomatous disease of humans and animals. This organism is commonly found in soil containing bird and bat manure.

Etiology- Dimorphic fungus Histoplasma capsulatum

Histoplasma capsulatum var.capsulatum

Histoplasma capsulatum var.duboisii

Occurrence in animals- Many species of domestic and wild mammals are susceptible to the infection. Infection appear most frequently in dogs with clinical symptoms.

Epidemiology- Worldwide distribution. More abundant in America than other continent. The H.capsulatum var.duboisii is known only in Africa. Distribution of fungus in the soil is not uniform. Most of the cases occurred in people who for occupational, educational or recreational reasons had visited caves, abandoned mines and tunnels in which bat droppings had accumulated. The disease appears sporadically or in epidemic outbreak. There are also endemic regions in Latin Americas. In Mexico, epidemic outbreak or isolated cases of the disease has been recorded; 11 outbreak affecting 75 people in 1979 and 12 outbreak affecting 68 people in 1980. In Africa, there are some 200 known cases of histoplasmosis due to duboisii variety.

Source of infection and mode of transmission– The reservoir of the agent is soil contaminated with bird or bat droppings.

Man and animal acquire the infection from the same source (soil) through inhalation. Microconidia of the fungus are the infecting elements.

Disease in animals– Lungs and thoracic lymph nodes are primary site of infection. GIT is the primary site of infection especially in dogs. Organism enter blood stream from primary focus and disseminated throughout body. Organism may localize in bone marrow or eyes leading to Chorio-retinitis or Endophthalmitis. Mainly symptoms are non-specific.

• Dog: Weight loss due to emaciation, chronic cough, persistent diarrhea, fever, anaemia, hepatomegaly, splenomegaly, lymphadenopathy and GI ulceration. Obstructive respiratory difficulty due to tracheobronchial lymphadenopathy. Dissemination may involve skin also with weeping, ulcerated and nodular lesions.

 

• Cat: Kittens one year of age or younger were most affected. Clinical signs same as dog. Disseminated infection common.

 

• Birds: They are not susceptible to histoplasmosis because their high body temperature does not allow the fungus to develop.

Disease in humans– Most infections occur asymptomatically. When conidia of fungus are inhaled, they can lodge in the bronchioles and alveoli. Incubation period from 5 to 18 days. There are 3 clinical form of disease:

1. Acute pulmonary form- Most frequent and resembles influenza, cough, and chest pain. This form of disease often goes unnoticed. In mild cases, recovery occur without treatment.
2. Chronic cavitary pulmonary form- occur most frequently in people over the age of 40 year with prevalence among males. This form resembles pulmonary tuberculosis with cavitation.

• Disseminated form- Most serious and seen primarily in very young or elderly, can be acute or chronic.

Acute- occur primarily among nursing babies. Hepatosplenomegaly, fever and prostration. Leukopenia, thrombocytopenia and anaemia are frequent.

Chronic pneumonia, hepatitis, endocarditis.

Disseminated histoplasmosis occur in immunodeficient patients. In African histoplasmosis, lesions occur most frequently on the skin, in subcutaneous tissue and bones.

Diagnosis

1. Microscopic examination of stained smears; immunofluorescence using clinical samples such as sputum, ulcer exudate and other material
2. Isolation in culture media

• Inoculation of mice

1. Disseminated histoplasmosis- by culturing blood, bone marrow, urine or through biopsy or through histopathology. Biopsy material stained with Silver Methenamine yields good results.
2. Serological tests- complement fixation, immunodiffusion, latex agglutination, but these are not very sensitive and specific.
3. Histoplasmin intradermal test (humans) – like tuberculin test and read at 24 and 48 hrs. It is advisable to administer the test together with the coccidioidin and blastomycin test because of cross reactions.

• In humans urine test is available that can check for recent infection from Histoplasma, by measuring the presence of antigen i.e. capsulatum polysaccharide antigen. EIA (Sandwich enzyme immunoassay) is used for this. EIA is more sensitive when urine rather than serum is tested. The amount of histoplasma antigen detected in urine can be used to monitor a patient’s response to therapy.

Treatment- Itraconazole @ 10mg/kg/day is the drug of choice for disseminated histoplasmosis in dog and cat. Ketoconazole can also be used @ 10-15mg/kg. In humans, oral Itraconazole can be used. Amphotericin B for 4 to 12 weeks.

Control– Reducing people’s exposure to dust by spraying with 3-5% formalin solution on the ground when cleaning hen houses or other potentially contaminated sites. Use of protective mask. During outbreak, eradicate the fungus from its natural force by spraying the soil with anti-fungal agent.

ASPERGILLOSIS (Pneumonomycosis/ Bronchomycosis)

Etiology- Aspergillosis species especially; Aspergillus fumigatus and Aspergillus terreus

Occurrence in animals– Almost all domestic animals, birds and many wild species are affected. The disease in cattle and fowl has economic implications. Primarily respiratory infection become generalized.

Epidemiology– Worldwide distribution as the fungus is ubiquitous. Disease has no particular distribution. Occurrence of aspergillosis in humans occur sporadically and is uncommon.

Source of infection and mode of transmission– The reservoir is the soil. Fodder and bedding contamination by the fungus is an important source of infection. Contaminated incubators, hatcheries, incubation rooms may be the source of infection for chicks or young turkeys.

Transmission occur by inhalation.

Disease in animals– Occur sporadically, primarily causes respiratory system disorders.

• Ruminants- Mycotic abortion in cattle. 75% of mycotic abortion are due to aspergillus. Mycotic abortion is seen mainly in stabled animals, thus it occurs during the winter in countries with cold or temperate climate.

Fungus localizes in lungs> enter blood stream> invade placenta causes placentitis > abortion, usually occur during the third trimester of pregnancy. Cotyledons swell and turn a brownish gray color.

Mycotic pneumonia rapidly fatal> signs are pyrexia, rapid shallow stertorous respiration, nasal discharge, moist cough.

• Horses- Guttural pouch mycosis. Epistaxis and dysphagia common complication. Mycotic rhinitis characterized by dyspnea and nasal discharge. Locomotor and visual disturbance when infection spreads to brain and optic nerve.

 

• Dog- Confined to nasal cavity or paranasal sinus. Mainly infection occur with fumigatus. Signs are lethargy, nasal pain, ulceration of nares, sneezing, unilateral or bilateral sanguino-purulent nasal discharge, frontal sinus osteomyelitis and epistaxis.

Gross lesions- mucosa of nasal and paranasal sinus covered by layer of black necrotic material and fungal growth. Nasal aspergillosis seen mainly in Dolichocephalic breeds. Lumbar disk spondylitis and focal osteomyelitis were common. Disseminated disease most common in German Shepherds.

 

• Fowl- Acute aspergillosis- occur in chicks and young turkey. Symptoms include fever, loss of appetite, labored breathing, diarrhea and emaciation.

Chronic aspergillosis- occur in adult birds sporadically. Yellowish granuloma of 1 to 3mm appear on lungs. Plaques develop in air sacs, bronchial tubes and trachea. Clinical forms other than pulmonary form occur in birds- dermatitis, osteomycosis, ophthalmitis and encephalitis.

Disease in humans– 2 clinical forms

• Localized- mainly respiratory system infection acquired through inhalation. Contract an acute and rapidly progressing pneumonia.
• Allergic bronchopulmonary aspergillosis (ABPA) – occur in patients with pre-existing asthma. ABPA patients may expectorate bronchial plugs in which hyphae of fungus can be detected microscopically. Intradermal (skin prick) test produces an immediate reaction to aspergillus antigens, with papules and reddening
• Fungus ball or aspergilloma- fungus mainly colonized respiratory cavities. This form is relatively benign.
• Otomycosis- caused by niger and invasion of paranasal sinuses.
• Cutaneous form- rare, appear in immunodeficient patients.
• Invasive form- very serious, occur only in patients with neutropenia

Diagnosis

1. Radiograph in dogs with nasal aspergillosis.
2. Visualization of fungal plaques by rhinoscopy.

• Isolation by culture, but it is not reliable test because aspergillosis is ubiquitous and can be isolated from nasal cavities of healthy dogs.

1. Serological test- agar gel double diffusion test, ELISA
2. Immunofluorescent procedures to identify hyphae in tissue sections.

Treatment

1. In dogs- Topical treatment— Clotrimazole and Enilconazole

Systemic treatment—- Ketoconazole and Itraconazole

1. In horses- surgical exposure and curettage. Topical natamycin and oral KI is also effective

• Bovine mastitis- intra-arterial and intra-mammary injection with Miconazole

Control– Adopt hygienic conditions. Moldy bedding or fodder should not be handled or given to domestic mammals and birds.

CANDIDIASIS (Moniliasis/ Candidosis/ Thrush/ Candidomycosis)

It is localized muco-cutaneous disease.

Etiology- Yeast like fungus Candida albicans. It is the normal inhabitant of nasopharynx, GI tract and external genitalia.

Occurrence in animals– Candidiasis is rare in cats, dogs and horses. Systemic candidiasis in cattle, calves, sheep and foals. Moniliasis in chicks and poults is common.

Epidemiology– Worldwide distribution in a variety of animals. Most frequent opportunistic mycosis in humans, occur sporadically.

Source of infection and mode of transmission– Most infection has endogenous source. The infection can be spread through contact with oral secretions, skin, vagina and faeces of sick individual. A mother with vaginal candidiasis can infect her child during child birth. An exogenous infection probably occurred due to indirect contact between patients in a hospital bone marrow transplant and an intensive care unit.

Disease in animals– Avian candidiasis is an infection of the upper respiratory system.

Acute– Nervous symptoms. The most frequent lesion found in crop and consists of plaques that resembles curdled milk and adhere lightly to mucosa. Acute form occurs mainly in young birds.

Chronic– In adult birds, causes thickening of crop wall on which yellowish necrotic material accumulates.

Oral candidiasis occur sporadically in calves, colts, lambs, swine, dog, lab mice and guinea pigs. Mastitis and abortion in cattle.  Arthritis in horses. Organism can penetrate keratinized epithelium thus causes marked keratinous thickening of tongue, oesophagus and rumen mucosa. Skin lesions and thrush have been described in cats.

Disease in humans– Candidiasis is always associated with debilitating disease or conditions such as diabetes, AIDS, TB, cancer and others. Various clinical forms are:

1. Mycotic stomatitis (thrush) – characterized by lightly adhering white plaques on the tongue and other parts of mouth.
2. Esophageal candidiasis– pain upon swallowing and sub sternal pain. It may or may not be an extension of oral thrush.
3. Gastrointestinal candidiasis– small intestine is most frequent site of infection. Ulcers occur in stomach and intestine.
4. Vulvovaginitis– vaginal discharge and pruritus vulvae.
5. Muco-cutaneous form– systemic infection occur through hematogenous transmission.

Diagnosis

1. Direct examination of lesions in nails, skin or mucous membrane.
2. Isolation of agent from blood, pleural or peritoneal fluid, CSF or biopsy material

• Serological test- immunodiffussion or double diffusion.

Treatment– Cutaneous candidiasis can be treated with Nystatin ointment or topical application of amphotericin B or 1% iodine solution. Fluconazole for disseminated candidiasis in foals.

Control- Infected individuals should be isolated from healthy ones. Strict hygiene measures should be established. In case of moniliasis outbreak in fowl, destroy all sick birds and administer copper sulfate (1:2000) in drinking water and Nystatin (110mg/kg) in feed.

RHINOSPORIDIOSIS

Chronic, non-fatal, pyogranulomatous infection

Etiology– Rhinosporidium seeberi. Organism not been cultured and its natural habitat is unknown.

Occurrence in animals– Horse, cattle, dogs, cats and aquatic birds.

Epidemiology– Seen often in India, Africa and South America. Disease has endemic zones in India and Sri Lanka. The disease is rare throughout the world.

Source of infection and mode of transmission- The natural habitat of the agent is unknown. In India and Sri Lanka, where most cases have been recorded, the source of infection has been associated with stagnant water. The route of infection or mode of transmission is also unknown.

Disease in animals and humans– The disease is characterized by pedunculated or sessile polyps on the mucous membrane particularly on nose and eyes. The polyps are soft, lobular and reddish with small white spots. They are not painful but they do bleed easily.

In humans these granulomatous formation can also be found in pharynx, larynx, eye, vagina, penis, rectum and on skin. The clinical picture in animals consist of chronic polypoid inflammation that may cause respiratory difficulty and sneezing. Epistaxis also noticed.

Diagnosis– Since fungus cannot be cultured, diagnosis depends on the clinical appearance of lesions. Stained histological preparation gives best result.

SPOROTRICHOSIS

Etiology– Sporothrix schenckii. It is a saprophytic fungus that lives in soil, plants, wood and decaying vegetation. It is also a dimorphic fungus.

Occurence in animals– Horses are the most frequently affected. Cases have been recorded in dogs, cats, rodents, cattle, swine, camels, birds and wild animals.

Epidemiology– Its occurrence is sporadic. It is more frequent in Asia, Brazil, and The Central American countries, Mexico, South Africa and Zimbabwe. The largest outbreak occurred in United States in 1988 in which 84 people were affected.

Source of infection and mode of transmission– The reservoir of the fungus are soil and plants. This fungus lives in soil, plants, woods and decaying vegetation. The source of infection is a gold mine epidemic which was a timber in South Africa on which S. schenckii was growing. Humans and animals almost always become infected through a cutaneous lesions. May also be transmitted through inhalation and is responsible for pulmonary sporotrichosis.

Feline sporotrichosis is known for its ability to transmit the infection to humans. Cats may carry decaying vegetation containing the fungus between their nails and may transmit the infection to other cats when they fight.

Disease in animals– Cutaneous lesions characterized by nodules and ulcers may be accompanied by lymphangitis. Nodules are painless, develop a scab, discharge a small amount of pus and heal in 3-4 weeks. Mainly nodules occur on the lower part of legs, usually about the fetlock. The disease in cats is of particular interest. Various symptoms are ulcerated nodules appeared on the eyes, behind the ears and in nose. The disease in dogs may manifest as the cutaneo-lymphatic form but it frequently affects the bones, liver and lungs.

Disease in humans– IP- 3weeks to 3 months. Common clinical forms:

1. Cutaneous form– nodule or pustule at the point of inoculation. Nodule may ulcerate and gray or yellowish pus appears.
2. Disseminated form– rare, localization in different organs, especially bones and joints as well as mouth, nose, kidneys and s/c tissue.
3. Pulmonary sporotrichosis– rare form of disease result from inhalation. Symptoms are cough, expectoration, dyspnoea, pleuritic pain and hemoptysis. The most frequent lesion in the lungs occur in the upper lobe.

Diagnosis- Culture and identification of the fungus. Direct immunofluorescence is specific and rapid method. Injection of pus into rats/hamsters: local lesion containing large no. of yeast like cells.

Treatment– Oral potassium iodide to treat cutaneous form. Itraconazole might be effective.

Control– Wood in industries where cases occur be treated with fungicides. Disinfection of bedding. Thorough washing of hands and arms with povidone iodine recommended for humans. Veterinarians and their assistant should use gloves to handle and treat cats with cutaneous lesions.

References:

• Centers for Disease Control and Prevention (CDC) http://www.cdc.gov/ncidod/dbmd/diseaseinfo
• http://homestead.org/RichardMonroe/ZoonoticDiseases/Fungi2.htm
• Acha PN, Szyfres B (Pan American Health Organization [PAHO]). Zoonoses and communicable diseases common to man and animals. Volume 1. Bacterioses and mycoses. 3rd ed. Sporotrichosis; p. 352-356, Aspergollosis; p.305-310, Candidiasis; p.315-319, Histoplasmosis; p.339-344, Rhinosporidiosis; p.350-352.