L16 Neglected Tropical Diseases

Define what is neglected tropical disease (NTDs)

• A group of diseases that cause devastating illness for more than 1 billion people, cause 53,000 deaths annually, cause disabilities

• “Neglected” because they have been largely wiped out 消滅了 in developed parts of the world, only persist in the poorest

Suggest a difference between protozoan infections and helminths infections

• Protozoan infections: Microscopic

• Helminth Infections: Seen naked eye

List 3 examples of protozoan infections

1. Leishmaniasis (VL, CL and MCL)

2. Human African trypanosomiasis (sleeping sickness)

3. Chagas disease

List 6 examples of helminth infections

1. Soil-transmitted helminth infections, Ascariasis, Ancylostomiasis (Hookworm)*

2. Lymphatic filariasis (elephantiasis)*

3. Onchocerciasis (river blindness)

4. Schistosomiasis*

5. Dracunculiasis (guinea-worm disease)*

6. Echinococcosis and other zoonotic helminthiasis

List 1 example of viral infections

• Dengue & dengue hemorrhagic fever(DHF)

List 3 examples of bacterial infections

• Leprosy 麻風

• Trachoma 沙眼

• Buruli ulcer

How does Dracunculiasis be transmitted ? How the disease affect the infected individual ?

Dracunculiasis (guinea-worm disease)

• The disease exists only in Africa and is transmitted exclusively by drinking contaminated water.

• Water> Intestine> Mating> Female migrate > GI> SC >limbs

Suggest 2 drugs that can treat against Lymphatic filariasis (elephantiasis)*

• Albendazole

• Ivermectin

What is Trachoma ? What is the infection agent for the disease ?

“Blinding” Trachoma

• An eye infection caused by bacterium Chlamydia trachomatis

• Spread by eye-seeking flies

• Children ages 1-9 and women has the greatest burden of disease

• Repeated infections scar the inner eyelid, eventually causing the eyelid to turn inward —> scratch the cornea —> irreversible blindness

What is Onchocerciasis ? What is the infection agent for the disease ?

• “River blindness”

• Infected by black fly

• Symptoms:

  • Skin rash, intense itching and skin depigmentation

  • Nodule

  • Infection and inflammation of cornea result in blindness

Trachoma or Onchocerciasis caused more proportion of global blindness ?

Trachoma: 12.5%

Onchocerciasis: 0.6%

What are the 3 form of Leishmaniasis ? Explain the disease

VISCERAL ( SERIOUS) : systemic organ failure

CUTANEOUS (COMMON): skin ulcers

MUCOCUTANEOUS: nose/mouth destruction

What is Schistosomiasis ? Suggest a drug for the disease

“Snail fever” caused by Schistosoma haematobium

• 個肚凸咗啲嘢出嚟

• Praziquantel

What is Buruli ulcer ?

A kind of Mycobacterium Ulcerans

• Same family as TB and leprosy

• MASSIVE DESTRUCTION OF THE SKIN AND, IN SOME CASES, OF BONE, EYES, AND OTHER TISSUES

• Limb amputations may be needed to save the Pt life

What is Leprosy ?

(Considered shameful and people hid their symptoms for fear of ostracism 排斥 despite free and effective multidrug therapy)

麻风病, skin

What is Dengue ? Suggest the transmission agent

• Dengue is transmitted by the bite of an aedes mosquito infected.

• Symptoms appear 3-14 days after the infective bite.

• Dengue fever is a febrile illness that affects infants, young children and adults.

• Symptoms range from a mild fever, to incapacitating high fever, with severe headache, pain behind the eyes, muscle and joint pain and rash.

Which NTD has the highest annual death in global ?

Schistosomiasis

What is Ascariasis ? Suggest the causative agent

Ascaris lumbricoides

• A intestinal nematodes —> causing intestinal obstruction

• Fecal-oral transmission, food or water exposed to contaminated soil

• fever during migratory phase

• inflammation of internal organs including pancreatitis and appendicitis

How to diagnose and confirm Ascariasis infection ?

Laboratory criteria
Microscopic identification of ascaris eggs in feces

Case classifications

Ultrasound showing worms in the pancreas or liver or CT scans or MRI showing worms present in the ducts of the liver or pancreas

Suggest drug choice for Ascariasis / Ancylostomiasis

Anti-helminthic

• albendazole

• mebendazole

What is Ancylostomiasis ? Suggest the causative agent

Hookworm infection (soil —> skin —> bloodstream —> lungs —> intestine)

• Primarily percutaneous by direct exposure to contaminated soil

• Oral and transmammary(Milking) transmission

  • No human to human transmission occurs with the rare exception of transmission from an infected mother to her fetus via breast milk

• symptoms:

  • Severe anemia

  • Growth and cognitive impairment in children

Ancylostoma duodenale and Necator americanus

How to diagnose and confirm Ancylostomiasis infection ?

• Microscopic identification of Ancylostoma or Necator eggs in feces OR

• Microscopic identification of Ancylostoma or Necator species of larvae cultured from the feces OR

• Identification of adult worms expelled after treatment
  

Describe the life-cycle of Echinococcus causing Echinococcosis

1. Intermediate hosts become infected by ingesting tapeworm eggs (e.g. Human)

2. Eggs hatch into larvae, migrate out of GIT and develop into cysts and tumors in various organs

3. Predators are the definitive hosts (e.g. dogs, canids 犬科動物, felids 貓科動物), They Ingest cysts within intermediate hosts, (through protoscolices (infected organs) the tapeworm completes its lifecycle in the GI and eggs are shed into the environment through their feces

How to diagnose and confirm Echinococcus infection ?

• Laboratory detection of cysts or tumors using imaging techniques

• Collection and examination of materials collected by biopsy or puncture during surgery

  • Hydatid cyst fluid

  • DNA detection by PCR of protoscoleces

Suggest the treatment for Echinococcus

• Surgery remains the most effective treatment to remove the cyst and can lead to a complete cure.

• The treatment of alveolar echinococcosis is more difficult than cystic echinococcosis and usually requires radical surgery, long-term chemotherapy, or both.

Suggest the global prevention strategies for Neglected tropical disease (NTD)

• Mass chemotherapy Program (MDA): primary treatment and control of soil born Helminth disease, three vectors borne and bacterial Trachomas

  • Use cocktails of several antiparasitic and antibacterial drugs

• Safe water and Sanitation programs: education

• Vector control (e.g. use of insecticide)

• Case detection and management

• Vaccination

What is Human African trypanosomiasis (sleeping sickness) ? Also, suggest a treatment for it

• It is caused by bite of tsetse fly

• Treatment: Melarsoprol or Eflornithine (IV Kit) 脫毛膏都係呢個名

List the NTD that adopted large scale intervention in order to improve access (7)

• Lymphatic filariasis

• Leprosy

• Onchocerciasis

• Schistosomiasis

• Helminthiasis

• Trachoma

• Yaws

List the NTD that adopted case management and development of new tools, this focused intervention improve innovation

• Human African trypanosomiasis

• Chagas diseases

• Buruli ulcer

• Leishmaniasis

• Dengue