Nematodes: Key Pathogens and Clinical Manifestations Explained

Nematodes like *Toxocara canis* and *Onchocerca volvulus* cause significant health issues, including blindness and skin disorders.

### Understanding Four Key Tissue Nematodes: Toxocara canis, Onchocerca volvulus, Loa loa, Wuchereria bancrofti
* 🐶 The first nematode, *Toxocara canis*, is transmitted fecal-orally, primarily affecting **children who come into contact with infected soil or sandboxes**, leading to symptoms such as **blindness and meningoencephalitis**.
* 👁 Key clinical manifestations include ocular larva migrans, which results in **unilateral vision loss**, and visceral larva migrans, causing infections in organs like the liver and spleen, with **hepatosplenomegaly** being a notable symptom.
* 🌊 Next, *Onchocerca volvulus*, known as African river blindness, is transmitted by black flies and causes **blindness and dermatitis** due to immune reactions against the **adult worms and microfilaria** present in the eye and skin.
* 👁 Symptoms of *Onchocerca volvulus* include **recurrent conjunctivitis**, **progressive visual loss**, and skin conditions such as leopard skin, marked by **pruritis and skin depigmentation**, with treatment involving **Ivermectin**.
* The third nematode, *Loa loa*, or the African eyeworm, is transmitted by deer and mango flies, leading to **painful vision without vision loss**, characterized by **angioedema and pruritus** as the worm migrates through the subcutaneous tissue.
* 👀 The visual symptoms of *Loa loa* arise from the worm's presence in the **subconjunctival tissue**, making it **visually identifiable**, whereas its differentiation from *Onchocerca volvulus* hinges on the **absence of blindness**.
* 🐘 Finally, *Wuchereria bancrofti*, transmitted by mosquitoes, is the **second leading cause of infectious disability globally**, leading to lymphatic filariasis characterized by **lymphedema, adenolymphangitis, and the severe manifestation of elephantiasis**.
* 🏦 The mnemonic for *Wuchereria bancrofti* relates to a "**bank**" and an "**elephant piggy bank**," linking it to the **severe swelling and hyperpigmentation** associated with elephantiasis, with treatment also being **diethylcarbamazine**.

Nematodes (TISSUE parasites)

Dirty Medicine

Introduction to Tissue Nematodes and Learning Strategy

Focus on four tissue nematodes: *Toxocara canis*, *Onchocerca volvulus*, *Loa loa*, and *Wuchereria bancrofti*.

Emphasis on simplification using buzzwords, associations, and pneumonics for efficient learning.

Prioritization due to the greater emphasis on bacteria and viruses in exams.

Introduction of *Toxocara canis*, its association with canid animals, and fecal-oral transmission.

Toxocara canis: Transmission, Risk Factors, and Symptoms

Risk factors include tropical/subtropical climates and community sandboxes.

Children are at higher risk due to contact with infected soil or sandboxes.

Main symptoms: blindness and meningoencephalitis.

Disease processes: ocular larva migrans (unilateral vision loss), visceral larva migrans (hepatosplenomegaly, heart, other organs involvement), and central nervous system involvement (meningoencephalitis, neuropsychiatric symptoms, seizures).

Treatment: bendazole.  Mnemonic: Canids use eyes and brains to hunt.

Onchocerca volvulus: Transmission, Symptoms, and Treatment

Also known as African river blindness; black fly (*Simulium damnosum*) as vector, prevalent near rivers.

Key symptoms: blindness and dermatitis (immune reaction to adult worms/microfilaria).

Pathophysiology: iNOS modification, increased pro-inflammatory interleukins (IL-1, IL-4).

Visual symptoms: conjunctivitis, keratitis, photophobia, visual loss. Skin symptoms: "leopard skin" (pruritis, papular/lichenified dermatitis, depigmentation).

Treatment: Ivermectin. Mnemonic: "Ancho circus" (blind man and skin guy).

Loa loa: Transmission, Symptoms, and Treatment

Also known as African eyeworm; vectors: deerfly and mango fly.

Key symptoms: painful vision (no vision loss) and dermatological manifestations (angioedema, pruritus, urticaria).

Angioedema, pruritus, and urticaria due to worm migration through subcutaneous tissue; painful vision due to worm presence in subconjunctival tissue.

Treatment: diethylcarbamazine.  Often diagnosed visually.

Wuchereria bancrofti: Transmission, Symptoms, and Treatment

Spread by mosquitoes; second leading cause of infectious disability worldwide.

Adult worms reside in lymphatics; symptoms related to lymphatic drainage problems.

Lymphatic filariasis: lymphedema (lymph anasia, inflammation, dying worms), adenolymphangitis (fever, painful lymph adenopathy), and elephantitis (severe swelling, hyperpigmentation, hyperkeratosis).

Treatment: diethylcarbamazine. Mnemonic: "Bank" (elephant piggy bank).