Oncocercosis, is a disease popularly known as river blindness or prospector’s disease. It is a parasitosis caused by the parasite Onchocerca volvulus. The disease is transmitted when you are bitten by the fly of the genus Simulium spp which is also known as black fly or borrachudo mosquito, becuase it resembles the usual mosquito and it can be found in river banks.
The main sign and symptom of the disease is the presence of the parasite in the eyes which will cause progressive loss of vision. For this reason, the disease is also known as river blindness. However, oncoercosis can be asymptomatic for years and this makes its diagnosis difficult.
The biological cycle of Onchocerca volvulus can occur both in the fly and in man. In man, the cycle begins when the insects feed on the blood then they release the infected larvae into the bloodstream. This larvae will mature up and reproduce to release microphila, which will spread throughout the blood and attack various organs. It is at this places that they will develop and give rise to symptoms then begin a new life cycle.
The flies will become infectious when they sting a person that has microphylatics in the blood. This is because at the time of feeding, they will ingest the microphylatics, that will infect the intestines and attack the salivary glands. This will also increase the possibility of infecting other people when the insects feed on another person’s blood.
The release of microphila by an adult larvae takes about a year and this means that the symptoms of oncocercosis will begin to appear after 1 year of infection. The severity of the symptoms depend on the amount of microfilia in the blood. Moreover, the adult larvae can survive in the body for up to 12 years and the female can release approximately 1000 microfilia per day, and its life time is about 12 years.
Signs and symptoms of oncoercosis
The main symptom of oncoercosis is progressive loss of vision as a result of the presence of microphylatics in the eyes. If the disease is left untreated it can cause total blindness. Other signs and symptoms of the disease include:
- Oncocercoma: This corresponds to the formation of subcutaneous and mobile modules that contain the adult vermin. These nodules can attack the pelvic region, thorax and head. They are usually painless when the vermins are alive and when they die, the inflammatory process increases which causes a lot of pain.
- Oncodermatitis: It is also known as dermatitis which is characterized by loss of skin elasticity, atrophy and fold formation. This usually happens due to the death of the microphylatics that are found in the connective tissue of the skin.
- Eye lesions: These are irreversible lesions that are caused by the presence of microphilaria in the eyes that can cause total blindness.
Moreover, there may also be lymphatic lesions where by the micrphylaphyrias can reach the lymph nodes which are near the skin lesions and result to damage.
How to diagnose
It is difficult to diagnose oncoercosis at its early stages because the disease can be asymptomatic for man years. The diagnosis is made by examining he symptoms presented by the patient. Tests may also be done by the doctor which will help in confirming the diagnosis. These tests include ophthalmologic examinations and blood tests that involve the seeking the microphilics in red blood cells. The doctor may also request for an ultrasound so as to verofy the formation of nodules by the parasite; as well as performing other tests such as PCR which will identify Onchocerca volvulus.
Aside form performing these test, the doctor may also request a histopathological examination that involves biosating a small skin fragmentation so as to identify the microphylactics and exclude the occurance of other diseases such as adenopathies, lipomas and sebaceous cysts.
How treatment is done
The treatment of oncocercosis is done using anitiparasitic Ivermectin, a drug that is very efficient against microphile. This is because it is able to kill the parasites without causing any adverse side effects.
Despite the drug being very harsh against microfilia, Ivermectin does not cause any effect on the adult larvae. In such a case, it is necessary to remove the nodules containing adult larvae using surgery.
Prevention of Oncocercosis
The best way to prevent onchocerca volvulus infection is by using repellents and wearing the appropriate clothing especially in regions where the insect is prone to breed such as along riverbeds. You should also put in place ensure that are aimed at combating the mosquito such as using larvacides and biodegradable insecticides.
It is also recommended that the inhabitants of endemic regions or people who have visited regions where the insect is prone to breed should be treated using Ivermectin annually and every six months as a precautionary method to prevent oncocercosis