• The epidemiology of  Mansonella streptocerca is the study of the distribution, transmission, and impact of this parasitic worm infection in humans. According to the CDC, M. streptocerca is an Old-World species that takes place in West and Central Africa’s tropical regions. Within endemic regions, Mansonella spp. Transmission is typically highly focused, with considerable variations in local prevalence. Although uncommon, travel-related cases involving citizens of non-endemic nations have been reported. 
• streptocerca infection is transmitted by midges, which are small biting insects that live in tropical and subtropical regions of Africa and Asia12. The infection occurs when a midge bites a person and injects third-stage larvae into the skin wound. The larvae then develop into adults that live in the dermis and produce microfilariae (short-lived stage of the parasite) that circulate in the blood. The microfilariae can be ingested by another midge during a blood meal, completing the life cycle.
• The prevalence of  M. streptocerca infection in West and Central Africa ranges from 0.1% to 10%, based on the demographic being examined and the geographic area. The infection is more common in children than in adults and rural areas than in urban areas. 
• The mortality rate of  M. streptocerca infection is unknown, as there is no reliable data on the natural history or complications of the disease. However, some cases have been reported to cause severe skin lesions, lymphadenopathy, fever, headache, and eosinophilia. These signs could point to a severe infection that needs to be treated with medical attention and treatment. 
• The treatment of M. streptocerca infection is usually founded on empirical treatment with medications that are effective against other filarial infections, such as ivermectin (a macrocyclic lactone), albendazole (an anthelmintic), diethylcarbamazine (a benzimidazole), or mebendazole (a benzimidazole). Depending on the medication used and the patient’s response to therapy, the length of treatment might range from 4 to 12 weeks. 

• Kingdom: Animalia  
• Phylum: Nematoda (roundworms) 
• Class: Secernentea 
• Order: Spirurida 
• Family: Onchocercidae 
• Genus: Mansonella 
• Species: M. streptocerca 

structural characteristics of  Mansonella streptocerca: 

• Mansonella streptocerca is characterized by the presence of microfilariae in the blood. Microfilariae are the larval stage of the parasite and are sheathed, meaning they are enclosed in a protective membrane. 
• The microfilariae exhibit a unique morphology, with a coiled appearance, distinguishing them from other Mansonella species. 
• Adult Mansonella streptocerca worms reside in the subcutaneous tissues of the human host, typically in the connective tissue. 
• The adult worms are thread-like and have a slender, elongated shape. 
• Mansonella streptocerca exhibits a nocturnal periodicity, meaning that microfilariae are more likely to be present in the peripheral blood during the night and early morning hours. 
• Blood samples for diagnostic purposes are often collected during this nocturnal periodicity to increase the chances of detecting microfilariae. 
• The transmission of Mansonella streptocerca occurs through the bite of infected Culicoides midges. These midges serve as vectors for the parasite. 
• When an infected midge takes a blood meal from a human host, it introduces microfilariae into the bloodstream, continuing the life cycle. 

Antigenic types of  Mansonella streptocerca are the different forms of antigens (molecules that can trigger an immune response) that this filarial nematode can produce or express. Some of the antigenic types of M. streptocerca are:

• M. streptocerca-specific antigens: These are antigens that are unique to M. streptocerca and can be used to distinguish it from other filarial infections. For example, M. streptocerca has a specific antigen called MSA-2, which is a 31-kDa glycoprotein that is recognized by IgG4 antibodies in infected patients. 
• Cross-reactive antigens: These are antigens that are shared by M. streptocerca and other filarial or non-filarial parasites and can cause false-positive results in serological tests. For example, M. streptocerca has cross-reactive antigens with Onchocerca volvulus, Loa loa, Wuchereria bancrofti, and Brugia malayi, such as the 200-kDa antigen, the 42-kDa antigen, and the 32-kDa antigen. 
• Stage-specific antigens: These are antigens that are expressed by M. streptocerca at different stages of its life cycle, such as the microfilarial stage, the adult stage, or the larval stage. For example, M. streptocerca has stage-specific antigens that are detected by IgE antibodies in infected patients, such as the 14-kDa antigen (microfilarial stage), the 16-kDa antigen (adult stage), and the 22-kDa antigen (larval stage). 

The pathogenesis of Mansonella streptocerca infection is the process by which the parasite causes disease in humans. According to the web search results, the pathogenesis of M. streptocerca infection involves the following steps: 

• A midge (genus Culicoides) bites a human host and injects third-stage filarial larvae into the skin wound. 
• The larvae pierce the epidermis and go into the dermis, where they develop into adults that live near the skin surface. 
• The adult worms produce unsheathed microfilariae that go through the bloodstream and may be consumed by another midge during a blood meal. 
• The microfilariae reach the thoracic muscles of the midge and develop into first-stage larvae, then third-stage infective larvae, and finally migrate to the midge’s proboscis. 
• The infective larvae can infect another human when a midge takes a blood meal from them. 
• The pathogenesis of  M. streptocerca infection may change based on a number of variables, including the location, the population studied, and the presence of complications or co-infections. 

The host defenses to Mansonella streptocerca are the mechanisms that the human body uses to prevent or eliminate the infection by this filarial nematode. Some of the host defenses to M. streptocerca are: 

• The skin: The skin is the main barrier against the entry of M. streptocerca larvae into the body. The skin also contains immune cells and antimicrobial substances that can recognize and destroy foreign antigens, including M. streptocerca. 
• The blood: The blood is the medium for the transmission of M. streptocerca from one host to another through midge bites. The blood also contains antibodies, complement proteins, and eosinophils that can bind, neutralize, or damage M. streptocerca. 
• The lymphatic system: There are numerous vessels in the lymphatic system and organs that transport lymph fluid throughout the body. The lymph fluid contains immune cells that can produce and present antigens to other immune cells. The lymphatic system also contains macrophages and other immune cells that can engulf and digest M. streptocerca antigens or microfilariae. 
• The mucosal surfaces: The mucosal surfaces are the moist areas of the body that line the respiratory tract, gastrointestinal tract, urogenital tract, and other organs. The mucosal surfaces have a high concentration of immune cells that can trap or expel M. streptocerca antigens or microfilariae from the body. 

These are some of the host defenses to Mansonella streptocerca infection. However, these defenses may not be sufficient or effective against this parasite in some cases, especially when it causes severe symptoms or complications in humans. 

• Mansonella streptocerca is a species of filarial nematode that can cause human infections. According to the CDC, most infections by M. streptocerca are asymptomatic, meaning they do not cause any symptoms.
• However, some people may experience pruritus, which is itching of the skin, especially over the thorax and shoulders. Other possible skin manifestations include hypopigmented macules (dark spots), excoriations (skin abrasions), and lichenification (thickening of the skin). In rare cases, M. streptocerca can also cause lymph node enlargement, which is known as lymphadenopathy in the axilla or inguinal area.  

• The diagnosis of  Mansonella streptocerca infection is usually based on identifying microfilariae in skin snips or biopsies. Eosinophilia, which is an increased number of eosinophils (a type of white blood cell) in response to inflammation or infection, is common. 
• Assays related to serology, including the enzyme-linked immunosorbent assay (ELISA) or rapid diagnostic test (RDT), can also be used to detect antibodies against M. streptocerca antigens in blood samples. However, these tests may not be very specific or sensitive and may cross-react with other filarial infections or non-filarial diseases. 

The prevention of Mansonella streptocerca infection involves avoiding exposure to midges, which are small biting insects that transmit the parasite from one human to another.

Some of the preventive measures are: 

• Using insect repellents, such as DEET, on exposed skin and clothing. 
• Put on protective clothes, including long-sleeved shirts and trousers, to cover the skin. 
• Sleeping under mosquito nets or in screened rooms to prevent midge bites at night. 
• Eliminating potential breeding sites for midges, such as stagnant water or organic matter, by draining, cleaning, or covering them.
• There is no vaccine currently available for Mansonella streptocerca infection. 

• Mansonella Streptocerca: Another Filarial Worm in the Skin in Western Uganda – PMC (nih.gov) 
• CDC – DPDx – Mansonellosis