Home page » Flea pest control » Fly transmitted diseases part 1

Fly transmitted diseases part 1

Being one of the bigger insect groups that have regular contacts with humans, flies quite often are vectors for different bacteria, viruses, protists and other disease causing agents. Here we will take a look at some of the diseases transmitted by flies.

African Trypanosomiasis or sleeping sickness is caused by a parasite called Trypanosoma. There are two kinds of African trypanosomiases, each named for the region in which it is found and they are caused by different parasites. East African Trypanosomiasis is caused by Trypanosoma brucei gambiense while West African Trypanosomiasis is caused by Trypanosoma brucei rhodesiense. Both parasites are transmitted by the tsetse fly – Glossina. Several species of tsetse flies are known to transmit trypanosomes to humans, namely Glossina palpalis, G. morsitans, G. tachinoides, G. fuscipes, G. pallidipes. The highest risk to being bitten by tsetse fly is in rural savannah and forested areas and near areas of heavy vegetation by rivers and water holes. Fever, severe headaches, irritability, swollen lymph nodes, aching muscles and joints are common symptoms of sleeping sickness. If untreated, mental and nervous system changes (progressive confusion, personality changes, slurred speech) and heart failure occur. If left untreated, infection becomes worse and death will occur within several weeks or months.

Onchocerciasis or River Blindness is a worm infection transmitted by black flies (Simulium spp.) found in tropical Central and South America and Africa. A causative agent of this disease is a parasitic worm Onchocerca volvulus that can live in the human body up to 14 years. Onchocerciasis is called “river blindness” because the blackfly which transmits the disease swarms in fertile riverside areas that frequently remain uninhabited for fear of infection. When in human body, adult worms live in nodules and the female worms produce high numbers of first-stage larvae known as microfilariae. These migrate to the sub-epidermal layer of the skin where they can be ingested by female blackflies. When microfilariae get into internal tissues of the eye, they cause eye inflammation, bleeding and other complications that lead to blindness. Onchocerciasis is a major cause of blindness in many African countries – there are about half a million of blind people due to river blindness.

Loiasis is yet another form of filariasis, common in equatorial Africa and transmitted by the biting deer fly or horse fly – Chrysops spp. Loiasis is caused by microfilariae of parasitic worm Loa loa. Loiasis is the most frequently diagnosed blood filarial infection in travelers returning to North America and the United Kingdom from Africa. It takes around 12 month for symptoms to develop and they include fever, itching, and skin swelling. Migration of an adult worm to the eyes can also occur, that is the reason Loa loa is also called the "African eye worm". Filarial infections are often followed by eosinophilia. Humans are the only known natural reservoir of this parasite with estimated 2-13 millions infected with the Loa loa larvae.