• The epidemiology of Fusarium avenaceum in humans is not well understood but it is likely influenced by geographic distribution, climatic conditions, and agricultural practices. The fungus occurs globally in Europe, Asia, Africa, North America, and South America and its occurrence and toxicity may vary based on crop, cultivar, harvesting, and storage with processing methods. 
• This can cause rare superficial infections in humans like keratitis and onychomycosis. Invasive disseminated infections have not been much reported but it may occur in severe immunocompromised patients. Treatment and prevention depend on the disease type and severity with the availability of antifungal agents and control measures to reduce exposure and contamination of the fungus and its mycotoxins. 

• Kingdom: Fungi 
• Division: Ascomycota 
• Class: Sordariomycetes 
• Order: Hypocreales 
• Family: Nectriaceae 
• Genus: Fusarium 
• Species: Fusarium avenaceum 
• Fusarium avenaceum is a species belongs to Fusarium genus and Hypocreales order with Nectriaceae family. 
• This fungus is complex and filamentous with a unique structure: 
• The organism consists of a mycelium with a network of thread-like structures called hyphae which grow in a branching pattern. 
• The organism produces conidiophores are having cylindrical structures which are arising from the hyphae, conidia, and asexual spores. 
• Phialides are the subulate structures with a heel at the base that are responsible for producing conidia in Fusarium. 
• Conidia are single-celled and sickle-shaped with a foot cell at the base and a beak at the tip. 
• Conidia form grains composed of hyphae and host cells which is surrounded by a fibrous capsule and arranged in a radial pattern. 

• Fusarium avenaceum antigens includes its cell wall components and secreted proteins that can cause toxic effects in humans and animals.
• Some studies have reported specific antibodies against Fusarium antigens in patients with fusariosis. 

The exact pathogenesis of Fusarium avenaceum infection in humans is not fully understood but it involves several steps: 

• The fungus enters the skin through a small cut resembling a thorn prick which forms a primary lesion in the subcutaneous tissue. 
• Fungus produces black grains and hyphae where host cells surrounded by a fibrous capsule with a radial arrangement of hyphae. 
• The fungus affects the hosts inflammatory response which leads to granuloma through macrophages, lymphocytes, and fibroblasts. 
• Fungus spreads along lymphatic channels and blood vessels that causing secondary lesions in distant sites like bones, joints, eyes, and brain which potentially forming sinuses and fistulas for pus and grains discharge. 
• The fungus can produce toxins that impact the host’s immune system and hematopoiesis leading to leukopenia, anemia, and thrombocytopenia. 

• Fusarium avenaceum is defended by the innate immune system particularly neutrophils and macrophages recognize the phagocytose and kill fungus through oxidative burst, degranulation, and antimicrobial peptide release. However, these defenses are often impaired in individuals with compromised immune systems. 
• The adaptive immune system of T cells act as a host defense against Fusarium avenaceum but the evidence is limited and conflicting. Some studies suggest that Th1 and Th17 cells can enhance antifungal activity while others find no correlation between T-cell subsets and fusariosis outcome. The role of B cells and antibodies is also unclear with some studies reporting protective effects of specific or nonspecific antibodies while others find no association or detrimental effects. 

The clinical manifestations of Fusarium avenaceum infection depend on the entry portal, host’s immune status, and the extent of dissemination: 

• Keratitis in cornea caused by trauma or contact lens use resulting in eye pain, blurred vision, and discharge. 
• Onychomycosis is a nail infection that results in discoloration, thickening, and brittleness of the nails. 
• Sinusitis results in symptoms like nasal congestion, facial pain, and discharge. 
• Meningitis in the membranes of the brain and spinal cord causes fever, headache, stiff neck, and altered mental status. 
• Skin lesions includes nodules, cellulitis, and necrotizing fasciitis that can be localized or disseminated. 
• Sino-pulmonary infections are sinus and lungs infections leads to cough, chest pain, and hemoptysis. 
• Bone and joint infections are characterized by inflammation, pain, and reduced mobility in the bones and joints. 
• Endophthalmitis is an eye infection that causes pain, blurred vision, and loss of vision in the inner eye. 
• Endocarditis is a heart valve infection that can lead to fever, heart murmur, and embolic complications. 
• Bacteremia is a blood infection that causes fever, chills, and septic shock. 
• Mycotoxicosis is a poisoning agent caused by ingestion of food contaminated with Fusarium species leading to the symptoms like abdominal pain, diarrhea, and bone marrow depression. 

The diagnostic methods that can be utilized includes: 

• Culture is the gold standard for identifying Fusarium species but this has limitations like specialized media, slow growth, and contamination risks. It can be performed on various specimens. 
• Microscopy can diagnose Fusarium infection quickly by observing hyphae and conidia in clinical specimens or culture isolates but it doesn’t differentiate Fusarium avenaceum from other species or molds. 
• Histopathology can reveal Fusarium species invasion, host inflammatory response, and other infection causes but it is insufficient to identify Fusarium avenaceum at the species level. 
• Molecular methods are reliable for identifying this species by overcoming limitations of culture, microscopy, and histopathology. These methods are based on DNA amplification and sequencing or detection of specific DNA probes or primers providing accurate and sensitive results. 

The prevention of Fusarium avenaceum infection depends on the type, severity, and risk factors with general preventive measures including: 

• Handling potentially contaminated materials like thorns, wood, or grains required to use protective gloves, shoes, and clothing.
• This involves thoroughly cleaning and disinfecting any wounds or injuries that is infected by Fusarium species and promptly seeking medical attention if any signs of infection appear.
• It is advised to avoid contaminated food by Fusarium species if the individual has a history of mycotoxicosis or allergic reactions.
• Reduce immunosuppressive drugs and monitor immune status in high-risk patients those with hematologic malignancies, transplantation, and chronic diseases.

• The Genome of the Generalist Plant Pathogen Fusarium avenaceum Is Enriched with Genes Involved in Redox, Signaling and Secondary Metabolism | PLOS ONE 
• Pathogens | Free Full-Text | Molecular Identification and Characterization of Fusarium Associated with Walnut Branch Blight Disease in China (mdpi.com)