Mansonelliasis is a parasitic infectious disease caused by roundworms (nematodes). The most common clinical symptoms are skin rashes, arthritis and lymph outflow disorders. Helminthiasis is also characterized by fever, inflammation of the lymph nodes, and an increase in the size of the liver. The diagnosis of pathology consists in the detection of the pathogen in a blood smear. Treatment involves the use of etiotropic antiparasitic drugs, symptomatic therapy (desensitizing, analgesics, anti-inflammatory, antihistamines, etc.).
Mansonelliasis refers to nematodes affecting serous membranes. The description of this helminth and the pathology caused by it was first published in 1897 by the Scottish doctor Munson, after whom the pathogen was named. In 1929, the American parasitologist Faust confirmed Munson’s discovery. Helminthiasis is widespread in the countries of India, South and Central America. Mostly men (about 60% of cases) are over 55 years old. Pathology occurs year-round, the most common attacks of vectors (woodlice) on a person occur in the evening or morning, bites are mainly localized in the upper half of the trunk.
The causative agent of the infection is the nematode Mansonella ozzardi. Females of this species reach a length of 80 mm or more, the length of the body of the larva (microfilariae) is about 0.2 mm. The source of helminthiasis is sick people who become the final hosts of mansonella. The intermediate (larval) stage of the pathogen takes place in the body of blood-sucking woodlice (family of diptera), which are carriers of the disease. The emergence of woodlice occurs in moist soil, overgrown reservoirs, they are active at dusk and in windless weather. Other vectors of infection may be black flies of the genus Similium. Infection occurs with the bite and blood sucking of woodlice, theoretically it can be observed during blood transfusion, organ transplantation, the use of non-sterile instruments, syringes for medical and non-medical purposes. The risk group includes tourists, children, agricultural workers, hunters.
The pathogenesis of mansonelliasis has not been studied enough. When penetrating through the skin with the saliva of a woodlouse, microfilariae enter the bloodstream and lymph flow of the final host. Through blood and lymphatic vessels with fluid flow, larvae are transported to the mesentery of the intestine, pericardium, lymph nodes, joint cavities, connective tissue, where they are located before puberty. Adult helminth individuals retain their activity in the organs, multiply by releasing microfilariae into the blood. The circulation of larvae in the blood ensures further organ invasion of the parasite; a clear daily rhythm of the appearance of microfilariae in the bloodstream is not described. Together with the larvae, toxic products of helminth metabolism are released, which causes sensitization of the body. The process of invasive massive inflammation in the lymph nodes, spreading through the lymphatic vessels leads to violations of the lymph flow.
The conditional division of mansonelliasis by clinical manifestations is based on the classification according to the leading syndrome. The almost constant presence of microfilariae in the circulatory system for a long time can affect all organs; cases of isolation of the pathogen from the cerebrospinal fluid are described. There are the following types of the disease:
- Allergic. It does not have bright clinical symptoms, in a general blood test during a routine examination, it may manifest pronounced eosinophilia.
- Articular. There are pains, swelling, redness and forced restriction of movements in large joints.
- Cutaneous. It proceeds with the formation of itchy rashes on the skin, which disappear on their own after a while, then reappear.
- Mixed. The presence in the clinic of signs of damage to two or more organs and systems suggests a massive invasion or a long-term course of helminthiasis.
The exact duration of the incubation period is unknown, presumably ranges from a few days to six months. The symptoms are nonspecific, sometimes practically absent. Patients may complain of prolonged subfebrility (37.5-38 ° C), weakness, moderate headaches, the appearance of skin rashes, itching. Knee, elbow, ankle, wrist, shoulder joints increase in size, pains appear when performing habitual movements. The skin over the joints becomes hot and hyperemic. Patients spare limbs, take unusual poses to reduce pain. With the aggravation of lymphostasis, swelling of the legs and face forms, sensitivity decreases, the lower extremities become cool, their external outlines change, walking causes pain. Accidental injury of the skin and the occurrence of secondary bacterial purulent processes (phlegmons, abscess), which are difficult to treat due to impaired lymph circulation, are possible.
The presence of complications, first of all, indicates the prescription of the process and untimely medical care. Frequent consequences of mansonelliasis are hydrocele, elephantiasis, chronic arthritis of large joints, purulent lymphadenitis, furunculosis, erysipelas, keratitis. Isolated cases of penetration of mansonella into the cerebrospinal fluid are accompanied by the risk of neurocognitive disorders, inflammation of the meninges and brain matter.
Consultations of an infectious disease specialist, dermatovenerologist, rheumatologist are shown. If there are symptoms of central nervous system and eye damage, an ophthalmologist and a neurologist are required. An important part of the diagnostic search is a detailed collection of epidemiological anamnesis. Criteria to confirm the presumed diagnosis include:
- Objective inspection. Physical examination may reveal skin rashes (erythema, papules), scratching (visible criterion for the presence of itching), joint changes (edema, hyperemia, local hyperthermia, restriction of voluntary movements). Sometimes, palpation reveals a diffuse increase in sensitivity in the iliac regions. The presence of edema of the face, limbs, lymphedema is determined, in advanced cases – fibredema.
- Laboratory tests. A general blood test confirms leukocytosis with pronounced eosinophilia, basophilia, and increased ESR. Biochemical parameters are within normal limits; it is possible to increase the level of uric acid, CRP. Changes in the clinical analysis of urine are usually absent, in rare cases, clusters of eosinophils can be detected. Examination of articular fluid confirms the presence of nonspecific inflammation.
- Identification of infectious agents. PCR and blood filtration through a polycarbonate membrane are considered the most effective methods. It is possible to use microscopic examination of a thick drop, thin blood smears, the Nott method. Blood is seeded for sterility and hemoculture. Serological diagnostics is performed with antigens of other pathogens of filariasis and worm infestations.
- Radiation methods. Chest radiography is performed for indirect confirmation of pericarditis, exclusion of other pathologies. Signs of pericardial changes are visualized on ultrasound. Ultrasound diagnostics makes it possible to exclude lesions of the peritoneum, lymph nodes of other etiology (infectious, metastatic).
Differential diagnosis is carried out with other worm infestations (onchocerciasis, vuhereriosis, loiasis, acanthocheilonematosis, streptocerciasis, dirofilariasis, trichinosis), viral hepatitis B, chikungunya fever, erysipelas, tuberculosis, syphilis, allergic dermatitis, arthritis, pericarditis, peritoneal carcinomatosis, rheumatism, eczema, lymphogranulomatosis, psoriasis, chronic venous insufficiency, primary and secondary elephantiasis.
The therapy of the disease is carried out in a hospital setting only with a severe course of the disease, the presence of comorbid pathology, in childhood, during pregnancy. It is necessary to exclude the patient’s contact with the woodlice. Dietary recommendations are associated with the rejection of potential food allergens (citrus fruits, cocoa, nuts, and others), the use of a sufficient amount of liquid. Bed rest is necessary until the normalization of body temperature for two days. In the absence of severe pain, movement is not limited.
diethylcarbamazine was considered the main etiotropic drug for a long time, in 2018 studies ivermectin showed high efficacy (disappearance of microfilaremia in 99.9% of patients). Symptomatic treatment includes the use of desensitizing (chloride, calcium gluconate), detoxification (glucose, saline solution), antihistamines (chloropyramine, desloratadine), anti-inflammatory drugs, analgesics. Immobilization of joints to reduce pain is performed by tight bandaging, the use of bandages and orthoses.
Prognosis and prevention
The prognosis of helminthiasis is favorable, with timely detection and treatment, complete recovery occurs. Cases of death from mansonelliasis have not been recorded, the probability of an unfavorable outcome is higher among people with a long course of the disease, the addition of complications, decompensation of chronic pathology. Frequent asymptomatic course contributes to the prolonged presence of the pathogen in the body. Specific prevention (vaccination) has not been developed. Chemoprophylaxis of infection (diethylcarbamazine, ivermectin, doxycycline) is recommended for persons traveling to endemic areas. Non-specific prevention consists in the use of protective clothing, repellents, insecticides, drainage of swampy areas, sanitary protection of reservoirs. Mosquito nets on windows are ineffective, because woodlice can penetrate through the cells.