From the transmission, that is, transmitted by bloodsucking insects, helminthiases, onchocerciasis is the most dangerous in its consequences. In this disease, the organs of vision, skin and lymph nodes suffer. Larvae of the helminth, parasitizing the skin, cause its sharp changes, which are manifested in the disorders of pigmentation, the expression of the skin and thickening of its upper layer. Inflammation of the eyeballs leads to serious complications, which result in blindness.
In humans, onchocerciasis can provoke the development of arthritis, localized on the skin of abscesses and abscesses, damage to the bones of the skull, as well as the "elephantiasis" of the scrotum and legs. In addition, in men with neglected disease, leather bags are formed, hanging down to the knees in which there are enlarged femoral or inguinal lymph nodes. According to different data, 18 million to 50 million people suffer from onchocerciasis, and more than three hundred thousand people have lost sight. The disease is caused by onchocercias of the species O. volvulus, common in Africa, and O. caecutiens Brumpt, with a distribution area in South America.
Both of these species are morphologically and biologically very similar and represent a filamentary body, which is pointed at both ends. The length of onchocercias is between two and five centimeters, while females are larger than males. Their larvae are much smaller, and do not exceed 0.37 mm in length. The carriers are the females of Simulium. Onchocerca volvulus is mostly parasitic in the nodes located in the pelvic region or in the scapular region, and much less often on the head.
Symptoms of onchocerciasis
Infected when bitten by infected humans, midges attack mainly in the morning and in the evening. The incubation period lasts for up to a year, although the infection becomes noticeable due to the nodes formed under the skin, a few months after the invasion. The expression of the symptoms of infection depends on the extent of the lesion and includes:
- a rise in body temperature, reaching, in severe cases, forty degrees;
- severe headaches;
- weakening of the body;
- firm, flaky skin, rash.
The most characteristic sign of the presence of helminthic invasion are dense fibrous nodes under the skin up to 7 cm in size localized in different parts of the human body. A low level of infestation first appears in the itch, with the greatest intensity manifested at night in the genital area and thighs. The so-called filariotic scabies is so strong that it can lead to suicide, when a person is unable to withstand the torment.
Symptoms of onchocerciasis in addition to itching are manifested by papular rash, which is characterized by the formation on the skin of papules of different shapes, from thickened skin, in which the skin thickens and becomes like a crust of orange. At the same time, the skin that has lost elasticity becomes like a skin of a lizard, an elephant or a crocodile. With prolonged dermatitis on the lower extremities, genitals, in the groin or underarms, spots appear on the skin, the so-called."Leopard skin".At the late stages of the invasion, atrophy of the hair follicles and sweat glands occurs, with the appearance of a sagging skin and young people become like old men. In severe form of onchocerciasis dermatitis, recurrent erysipelas begins, which mostly affects young people.
The most dangerous in this disease is the penetration of the larvae of the filaria into the eyes. Mechanical damage to apples, intoxication products of their activities and allergic effects cause lacrimation, scarring, flushing, photophobia, swelling and pigmentation of the conjunctiva. The more parasites are in the organs of vision, the more serious pathological changes there occur.
In an early stage, the onchocerciasis of the eye is manifested by the opacity of the cornea, called snowball due to its similarity to snow flakes. When keratitis spreads from the margins to the center of the cornea, its lower edge is covered with a network of blood vessels. In this case ulcers and cysts are formed on the cornea. Spikes, formed around the dead larvae, change the shape of the pupil. Further changes lead to a clouding of the lens and ultimately complete loss of vision is possible. By the way, people who lost their eyesight as a result of helminth infection die twice as often as with other diseases.
Complications of helminthic invasion in lesions of the organs of vision are glaucoma, cataracts, atrophy of the optic nerve and chorioretinitis. When lesions with filarias with onchocerciasis of the lymph nodes are observed a slight increase, especially inguinal, both superficial and deep lymph nodes. As a result, the risk of a hernia - inguinal or femoral hernia - increases. Among other manifestations of infection with onchocercias, the development of a disease is possible, in which loss of adipose tissue and muscle atrophy with a fatal outcome occur.
The life cycle of onchocerciasis is very long and is up to fifteen years. Nematodes enter the digestive tract of midge with a bite of an infected person. Then, after 6-12, the larva grows in size in half and moves first into the buccal cavity of the midges and then into its proboscis. When a midge bites a person, the larva penetrates under the skin and migrates to the lymphatic vessels and the subcutaneous fatty tissue, where it becomes a sexually mature individual. Adult parasites live in knots( onchocercomes), connected in capsules, and there produce offspring. These nodules contain living and dead females intertwined in a tangle, and males of a parasite. Female helminth annually produce up to 1 million larvae.
Foci of onchocerciasis are located, as a rule, along rivers, so sometimes this disease is called "river blindness".In West Africa, the disease is prevalent among the rural population. Especially intensively, the invasion is widespread in the Volta River basin, where up to 30% of the population is affected. In Russia, there are isolated cases of invasion.
Diagnosis of onchocerciasis
The first sign of onchocerciasis are visually visible, mobile connective tissue nodes under the skin, tight to the touch. In addition, in favor of the disease, taking into account the epidemiological data indicate:
- manifestations of dermatitis;
- changes in lymphatic system;
- lesions of organs of vision of different degree.
To determine onchocerciasis in excised nodes or skin sections,
- is used to detect antibodies or to determine the type of antigen from a known antibody by the complement fixation reaction( RSK);
- Immunological Research Method( RPHA);
- test for the definition of filariasis( ELISA);
- intradermal allergic test.
In case of eye damage with onchocerciasis, an ophthalmologist is required. The use of laboratory and instrumental diagnostics makes it possible to distinguish onchocerciasis from other helminthiases, hypothavinoses( A and B), fungal skin diseases, leprosy.
Treatment of onchocerciasis
The main task is to prevent irreversible changes and alleviate the condition of the sick person. The main method of therapy is medication. However, if the onchocercias are located on the head, in the immediate vicinity of the eyes, then only surgical intervention is recommended. For the treatment of onchocerciasis, the main drug that is predominantly chosen is the semisynthetic macrocyclic lactone( Ivermectin);which very effectively affects the larvae.
With a single admission in an amount of 150 mg per kilogram of weight, it acts for six months, killing the larvae of parasites. Therefore, it is recommended to take it twice a year. Side effects in the form of patchy-papular rash, itching, urticaria are noted in no more than 10% of patients. The drug is not recommended for admission to children under the age of five, pregnant and lactating mothers, as well as in diseases of the central nervous system. The last restriction is associated with the possibility of penetration of the drug through the blood-brain barrier.
Another potent antiparasitic drug, Suramin, effectively affects adult helminth individuals, but has a strong toxic effect. In particular, this affects the normal functioning of the kidneys, so all the time you need to carefully monitor the kidneys. Suramin prescribe in the case when it is necessary to completely remove parasites from the human body and achieve full recovery.
The choice of a method for the treatment of onchocerciasis is carried out only by a highly qualified trained doctor and in a hospital setting. This is due to allergic reactions of the body to the death of parasites, a high degree of toxicity of the applicable chemical preparations and the possibility of their individual intolerance to humans. Depending on the severity of the course of the disease, different therapies are used - monotherapy or a combination of drugs, adding to the above list of diethylcarbamazine. To suppress the allergic reaction, glucocorticosteroids are prescribed.
If onchocerciasis is accompanied by the development of infection, then for sterilization of sexually mature parasites and the destruction of infectious foci, Doxycycline is prescribed a one and a half month course of 100 mg per day, with a single dose. Preventive measures consist in individual protection from carriers of microfilariae from infected people to healthy ones. In epidemiologically dangerous areas, preventive maintenance of onchocerciasis with a continuous reception of chemotherapy is carried out.