08e helminthic

Misc helminthic infections

Loiasis

• Filarial nematode Loa loa

• Transmitted by female Chyrosops fly (horse or deer fly)

  • When a human is bitten, the infected fly introduces filarial larvae onto the skin which then penetrate into the wound

  • These larvae mature into adult worms over 3-6 months → adult worms cause clinical disease.

  • The adult worms live in the subcutaneous tissue and can migrate to any part of the body

  • The adult worms produce thousands of microfilariae which are released into the bloodstream

• Endemic to West and Central Africa

• S/smx

  • Calabar swellings – localised transient subcutaneous swelling, preceded by local pain/itch. Non-erythematous.

  • Ocular smx – conjunctiva is affected when the adult worms migrate and crawl beneath the conjunctiva. Causes inflammation and oedema.

    • Can be observed crawling across the eye! Cool article with video – Kalbitz S, Grünewald T. Loiasis. N Engl J Med 2021;385. https://doi.org/10.1056/NEJMicm2101227.

  • Others: encephalopathy, cardiomyopathy, nephropathy, arthritis, lymphadenitis

    • Encephalopathy in particular is a/w post-microfilaricidal treatment in patients with high levels of microfiliriae.

• Ix: Clinical – especially if migrating adult worms are seen, or Loa loa is seen on blood smear.

  • Bloods (FBC) – high eosinophil count

  • Blood smear – perform between 10am to 2pm (highest count) → also allows for quantification, which is important before starting tx

• Mx:

  • Reduction of microfilariae count – albendazole (if >20,000/mL), ivermectin (2500-20,000/mL)

  • Definitive treatment when count <2500/mL (killing worms and microfilariae) – diethylcarbamazine (DEC)

    • Can cause side effects such as fever, headache, myalgia, etc.

    • ✌🏻 albendazole – may require long course for definitive tx.

    • If loiasis co-occurs with onchocerciasis (see 05.05), do not give DEC (Mazzotti reaction – severe inflammation of skin and eyes)