Etiology and pathogenesis
Sources of infection include infected humans as well as certain animals (monkeys, dogs, and cats). Pathogen transmission is carried out by mosquitoes of the genera Anopheles, Culex, and others. Inside the vector insect, microfilariae develop within 8–35 days.
Upon entering the human body, adult helminths settle in the lymphatic pathways. Their active growth creates a mechanical barrier to lymph flow. Over time, partial or complete vascular obstruction develops, up to the blockade of the thoracic duct. Long-standing lymphostasis triggers irreversible fibrous changes in tissues.
Specific lymphangitis
A distinctive feature of filariasis is the atypical course of lymphangitis. Unlike standard bacterial infections, the process has several striking differences:
- Retrograde spread: inflammation proceeds from the proximal (central) parts of the limb to the distal parts.
- Absence of entry portal: there are no traces of primary trauma or infection on the skin.
- Absence of a primary focus: there is no purulent abscess from which the inflammation would originate.
During the prodromal period, patients note enlargement of the inguinal and axillary lymph nodes, and an itchy rash appears on the body. The affected lymphatic vessels are palpable as painful, dense red cords. The lymph nodes themselves are also dense and acutely painful upon palpation.
Stages of disease development
The disease develops over years and is accompanied by general symptoms of intoxication: fever, weakness, and headache. There are three main stages:
- Initial stage. Manifests with urticaria. Acute inflammatory symptoms may subside, but inevitably recur months or years later.
- Stage II (after 2–7 years). Persistent lymphostasis develops. Lymphatic vessels become varicosely dilated, and their rupture is possible. The patient experiences chylous diarrhea and lymph leakage (lymphotorrhea). Lymph nodes increase markedly in size. Against this background, pyogenic microflora often joins in, causing abscesses and phlegmons.
- Stage III. Elephantiasis (elephantiasis) develops. Most often, the lower extremities and scrotum are irreversibly enlarged; somewhat less frequently, the pathology affects the vulva, mammary glands, and upper extremities.
Diagnostics and treatment
The diagnosis is based on the clinical presentation and mandatory laboratory confirmation—the detection of microfilariae in the patient's blood.
Conservative therapy is effective in the early stages. The main drug is diethylcarbamazine (0.1 g three times a day for 7–10 days) under the control of blood tests. If a secondary infection joins, antibacterial therapy is prescribed.
Surgical treatment is indicated for acute purulent complications (peritonitis, pleural empyema) and for the correction of elephantiasis. Surgery for elephantiasis involves the radical excision of altered skin, subcutaneous adipose tissue, and fascia. The resulting defect is closed with split-skin grafts taken from healthy areas. In case of scrotal lesions, the tunica vaginalis of the testis and altered tissues are excised within healthy borders.
A critical condition before any surgery: according to repeated blood tests, there must be no microfilariae in the blood. Otherwise, preliminary medical deworming is indicated.
Briefly: answers to topical questions
Which genera of mosquitoes are vectors of filariasis pathogens?
Vectors of filariasis pathogens are mosquitoes of the genera Anopheles, Culex, and Aedes. Mosquitoes of the genus Mansonia transmit brugiasis pathogens. The development of microfilariae in the mosquito's body lasts 8–35 days.
Which species of filariae parasitize predominantly in the subcutaneous adipose tissue and eye tissues?
Loa loa—the African eye worm, the causative agent of loaiasis—parasitizes in the subcutaneous adipose tissue and under the conjunctiva of the eye. Adult Onchocerca also localize in the subcutaneous tissue; in immune individuals, they form onchocercomas.
To memorize the typical localization of elephantiasis in filariasis, use the "Lower Floor" rule: in the overwhelming majority of cases, the lower extremities and external genitalia (scrotum, vulva) are affected.
Class and exam questions
Which types of filariasis are most significant for the surgeon?
Wuchereriasis and brugiasis are of primary surgical interest. It is they that lead to severe lymphatic blockages and elephantiasis.
What is the main difference between filarial lymphangitis and common bacterial lymphangitis?
Inflammation spreads retrogradely (from the center to the periphery), while the entry portal of infection and the primary purulent focus on the skin are completely absent.
What condition is mandatory before plastic surgery for elephantiasis?
Repeated blood tests must confirm the complete absence of parasites. If microfilariae are detected, surgery is postponed until successful deworming is performed.
What else to study on this topic
- Chylous diarrhea and lymphorrhea: mechanisms of development against the background of deep blockade of lymph flow.
- Differential diagnosis of filarial and erysipelatous (bacterial) inflammation.
- Technique of split-skin grafting in the surgical treatment of elephantiasis.
- Features of blood sampling and methods of laboratory search for microfilariae.
- Principles of treatment of purulent complications (pleural empyema, peritonitis) against the background of severe helminthiasis.
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