Aspergillosis: Diagnosis, Prevention & Treatment

• Zoonosis is any disease or infection that is naturally transmissible from vertebrate animals to humans, according to the World Health Organization.

Overview of Zoonosis

• Many zoonotic pathogens are potential bio-weaponization agents, such as anthrax and glanders.
• A wide variety of animal species can act as reservoirs of pathogens, posing challenges to public health surveillance, prevention, and control of zoonotic diseases.
• Awareness of zoonoses benefits occupationally at-risk groups like farmers, pet owners, and veterinarians.

Classification of Zoonosis

• Categories of zoonoses can be based on etiological agents, reservoir hosts, the transmission cycle, and the ecosystem in which pathogens circulate.
• Viral, bacterial, fungal, and parasitic zoonoses are classifications based on etiological agents.
• Classification based on the reservoir host(s) considers the life cycle of the infecting pathogen.
• Zoonoses can be classified as anthropozoonoses, zooanthroponoses (reverse zoonotic disease transmission), and amphixenoses based on reservoir hosts.
• Transmission occurs through reservoir hosts, intermediate hosts, or insect vectors.
• The direct zoonoses disease transmission is perpetuated in nature by a single vertebrate species; examples are anthrax, rabies, and Q fever.
• Cyclozoonoses require two or more vertebrate hosts to complete the transmission cycle, with obligatory and non-obligatory types. Metazoonoses require both vertebrate and invertebrate hosts

Major Transmission Routes of Zoonoses

• Zoonoses can transmit directly or indirectly.
• Indirect transmission occurs through vehicles like contaminated air or water, vectors like mosquitoes, or inanimate objects.
• Direct transmission include animal bites and scratches, contaminated animal food products (due to improper handling and cooking), and feco-oral transmission
• Other major tranmission routes include vector-borne and air-borne transmission as well as indirect transmission through contaminated soil or water sources.

Zoonotic Infections

• Zoonotic infections are responsible for severe socio-economic losses, affecting global food security networks and increasing public health threats.
• Endemic zoonoses account for the majority of human illnesses and reduce livestock production in many areas worldwide.
• Viruses, particularly RNA viruses, are a significant proportion of emerging infectious diseases due to their ability to infect new host species with short generation times.
• Emerging infectious diseases are those that have not occurred before, have occurred previously but affected small numbers in isolated places, or have occurred throughout human history but have only recently been recognized as distinct diseases.
• Neglected zoonotic diseases affect mainly poor and marginalized populations in low-resource settings, including rabies, echinococcosis, taeniasis/cysticercosis, and schistosomiasis.
• Transboundary animal diseases (TADs) are epidemic in nature, highly contagious or transmissible, and have the potential for very rapid spread, irrespective of national borders, causing socio-economic and public health consequences.
• Contributing factors to outbreaks of TAD's include globalization, land encroachment, and climate change.
• Examples of TAD's include brucellosis, bovine tuberculosis, parasitic illnesses, anthrax, bovine spongiform encephalopathy, and influenza viruses.

Factors Responsible for the Emergence of Infectious Diseases

• Ecological changes
• Human demographics and behavior
• Technological developments
• Industrialization and agricultural activities
• Unsustainable economic development and land use
• International trade and travel
• Commerce-related activities
• Military expeditions and wars
• Microbial adaptation and change
• Breakdown of public health measures due to natural or man-made calamities
• An endemic disease has a habitual presence within a given geographic area, or is a usual occurrence of a particular disease within a given area.
• An epidemic is the occurrence of a disease above the normal expectancy in a region or country.
• A pandemic is a worldwide epidemic covering larger geographical regions.

Aspergillosis

• More than 250 species of Aspergillus exist, but fewer than 40 cause infections in humans.
• Aspergillus fumigatus commonly causes serious and invasive infections in humans, primarily in immunocompromised individuals.
• A saprophytic and ubiquitous air-borne fungus whose natural ecological niche is the soil.
• Infections in both animals and humans are rare and mainly occur in immunocompromised individuals; transmission from animals to humans is rarely reported.
• Inhalation of spores is the most common route of entry for aspergillosis, but can also affect the gastrointestinal tract and skin.
• Major risk factors for invasive aspergillosis in humans include prolonged neutropenia, long-term corticosteroid therapy, organ transplantation (bone marrow) and hereditary neutrophil dysfunction.
• In animals, aspergillosis can present as a respiratory infection.
• In dogs and cats, aspergillosis causes sinonasal, bronchopulmonary, and disseminated infections.
• In ruminants causes mycotic pneumonia, gastroenteritis, mastitis, placentitis, and abortion (A. fumigatus).
• In poultry linked to significant deadly outbreaks of domestic and free-ranging wild birds.
• Horses can develop guttural pouch infections, keratomycosis, and pneumonia.
• Depending on the patient's immune status, aspergillosis in humans can present as acute invasive aspergillosis, chronic or allergic bronchopulmonary aspergillosis (ABPA), or aspergilloma.
• The invasive form of aspergillosis principally involves the sinopulmonary tract.
• Immunocompetent patients can have allergic responses and chronic noninvasive forms of aspergillosis infection.
• The development of a fungus ball (aspergilloma) can develop to chronic inflammatory and fibrotic processes (chronic pulmonary aspergillosis).
• Vascular invasion causes pleuritic chest pain or hemoptysis.
• Disseminated aspergillosis affects the central nervous system causing seizures or neurological signs.
• Radiographic findings may not be confirmatory
• Diagnosis of aspergillosis is confirmed by culture and microscopic examination, which is the gold standard but lacks sensitivity.
• The specific etiological agent should be isolated to diagnosing Aspergillosis.
• Diagnosis can also provide information for antifungal susceptibility testing of Aspergilliosis.
• Clinical specimens collected for diagnosis include bronchoalveolar lavage (BAL), biopsies, and sputum.
• Histological demonstration of invasive hyphae or a positive culture from a normally sterile environment indicates invasive fungal disease.
• Environmental infection control guidelines can help reduce mold exposure; antifungal prophylaxis is for at-risk groups.
• At-risk groups should avoid activities that involve close contact with soil or dust, such as yard work or gardening.
• Treatment involves targeted systemic antifungal treatment for immunocompromised individuals, using medications such as voriconazole or isavuconazole (invasive aspergillosis), liposomal amphotericin B (alternative), and posaconazole and echinocandins (salvage treatment).

Coccidioidomycosis

• Coccidioidomycosis, also known as Valley fever, Desert rheumatism, San Joaquin fever, or California disease, is endemic to the semi-arid to arid life zones in the southwestern United States, Northern Mexico, and scattered areas of Latin America.
• The etiology of coccidioidomycosis is caused by Coccidioides immitis and Coccidioides posadasii.
• Coccidioides is Dimorphic; it has a mycelial form or has spherules (sac-like cells that give rise to endospores)
• Limited to the San Joaquin Valley in California and parts of Arizona; C. posadasii has a more widespread geographic distribution in the Americas.
• Endemic regions are typically dry and arid, characterized by hot summers and short winters with limited rainfall.
• Transmission has also been reported by contaminated fomites (dusty clothing and farm products).
• Dangerous to laboratory personnel and epidemics have resulted from inadvertent opening of culture plates.
• Dogs are the most severely affected, Cats, rodents, cattle and sheep can develop naturally acquired infections.
• Clinical outcomes in dogs include: subclinical infections, mild-to-severe primary pulmonary disease and disseminated disease.
• In animals, osteomyelitis is the most common form of disseminated disease in dogs, (skin lesions are present in cats).
• In cattle, coccidioidomycosis resembles tuberculosis with nodular lesions in the bronchial and mediastinal lymph nodes.
• Horses can experience disseminated infection and abortion, animal-to-human transmission is considered rare.
• In humans coccidioidomycosis, is typically a self-limited illness presented with cough, fever, chest pain or fatigue, and may be asymptomatic with 60% of primary infections.
• It typically presents as acute and chronic pulmonary disease, but may also disseminate widely to to the cutaneous, osseous and central nervous system.
• Risk factors for severe coccidioidomycosis include adults over 65 years, pregnant women, transplant recipients and people with underlying immunosuppressive conditions and Certain ethnicity (i.e. African Americans and Filipinos)
• Diagnoses: Disseminated disease commonly affects the musculoskeletal system, soft tissues and meninges in high risk patients.
• Diagnostic serological testing (antibody and antigen detection), including Detection of tube precipitin antibodies (IgM) against polysaccharide antigen.
• Complement-fixing IgG antibodies (chronic stage).
• Other diagnostics such as Polymerase chain reaction (PCR) on body fluids or tissue can be performed.
• Diagnosis is definitive with culture and is found via histopathological examination.
• Large spherules can be observed sputum samples or bronchoalveolar lavage fluid or smears from skin lesions.
• It ia classified as a bioterrorism agent; mold form is highly infectious and must be handled using biosafety level 3 precautions.

Prevention and Control

• Prevention is done via public awareness → endemic regions and among groups at risk for severe diseases.
• Prevention practices avoid spending time in dusty places like construction or excavation sites, and avoid activities that involve close contact with dirt or dust such as gardening and digging.
• Treat with wound cleaning skin injuries well with soap and water
• Treatment may need to involve Fluconazole, Itraconazole, Posaconazole and Amphotericin B.
• Reactivation of primary infections can occur in HIV-positive or immunocompromised hosts

Cryptococcosis

• Cryptococcosis is an opportunistic fungal infection with a worldwide distribution.
• Considered a leading cause of meningitis in HIV patients.
• The etiology of cryptococcosis is caused byC. neoformans and C. gattii (commonly associated with human cryptococcosis).
• This has five serotypes based on structural differences in the polysaccharide capsule and is a Encapsulated, melanin-forming, basidiomycetous yeast that exists as a saprobe in nature
• It's commonly linked to soil with nitrogen-rich guano (pigeon excreta); C. gattii is mainly found in decaying woods and other plant materials
• C. neoformans is commonly associated with immunocompromised AIDS patients and immunocompetent patients are at more risk of infections caused by C. gattii.
• Causes CRYPTOCOCCAL MENINGITIS which is a major opportunistic infection in HIV patients (over 80% mortality).
• There has been an increase in the number of cases observed in NON-HIV PATIENTS, these are with hematological malignancies, organ transplant recipients and patients affected by autoimmune diseases.
• It is transmitted when the yeast in the lungs, acquired from a environmental source via Soil contaminated with avian guano
• Transmission via exposure in the lungs can spread where is colonizes the respiratory tract and penetrates the pulmonary alveoli and disseminates through the bloodstream causing soft tissue infections, pneumonia and most often meningoencephalitis In immunocompromised individuals as well as by inoculation of the yeast into the skin. In Immunosuppressed individuals the infection has become reactivated and has caused disseminated infections

Disease in animals

• Begins with the involvement of the nasal cavity, paranasal tissues and lungs which disseminates into different organs (skin, eyes and central nervous system)

Explore aspergillosis, its diagnostic gold standard, and the most affected anatomical system. Learn about preventative measures in at-risk individuals and clinical signs of CNS involvement. Understand the risks and treatments associated with different forms of aspergillosis.