EPIDEMIOLOGY AND CONTROL OF HELMINTHIC INFESTATION

1. EPIDEMIOLOGY AND CONTROL OF HELMINTHIC INFESTATION Dr. Igbinedion MBBS, MPH,FRSPH

2. ASCARIASIS • It is caused by Ascarislumbricoides • It is the largest parasitic roundworm of man • It is one of the most common parasites in the world • Transmitted via soil • It has a worldwide distribution with high number of cases in sub-Saharan Africa, China and East Asia • Poor sanitation, low socioeconomic status, malnutrition and warm moist climate are factors that increase prevalence of this infestation • Ascarissuum causes infection in pigs. It is morphologically indistinguishable from A. lumbricoides so pigs are also reservoir of infection

3. ASCARIASIS (contd) • LIFE CYCLE • Host contact infection through the faecal-oral route • When infective eggs are ingested, the larva hatch in the small intestine • The larva then migrate to the caecum and proximal colon where they penetrate the mucosa • They then migrate to the liver through the portal blood • From the liver, there is migration of the larva to the lungs • In the lungs, the larva penetrate the alveolar spaces into the pharynx, where they are swallowed and subsequently return to the small intestine • Ascaris females can lay up to 200,000 eggs • Adult worms can remain in the intestine for about 1 year

4. ASCARIASIS (contd) • CLINICAL FEATURES • Mostly asymptomatic • Children have a higher intensity of infection than adults • Loss of appetite, impaired weight gain • Lung involvement- acute respiratory inflammation, difficulty in breathing and fever • Abdominal pain and distension, nausea and diarrhea • Intestinal obstruction from entangled adult worms • DIAGNOSIS • By identification of Ascaris eggs in a stool sample using a microscope

5. ASCARIASIS (contd) • CONTROL • Health education • Improving sanitation and personal hygiene- especially handwashing. This is a long term control measure that helps interrupt transmission and prevent re-infection • Proper disposal of faeces at home and in the community • Antihelminthics- This helps reduce morbidity. Drugs of choice- Albendazole and Mebendazole for 1-3 days. This can be used for prevention and treatment of infection

6. TRICHURIASIS • Also known as Whip worm infection • Caused by Trichuristrichuria • Transmitted by soil • Spread is faecal-oral • Worldwide distribution • More in the Tropics, where there is poor sanitation and in children • It has a lighter intensity of infection than Ascariasis • Man is the principal host but infection has been reported in monkeys, pigs and horses

7. TRICHURIASIS (contd) • LIFE CYCLE • Unembryonated eggs are passed in the faeces into the soil where they later become embryonated • Eggs become infective between 15-30 days • Embryonated infective eggs are then ingested through the mouth • The larva hatch in the small intestine • Larva grow to become adult worms in the colon, residing in the caecum and ascending colon • Adult worms have a lifespan of 1 year • Female worms may produce 3000-10,000 eggs/day

8. TRICHURIASIS (contd) • CLINICAL FEATURES • Asymptomatic in light infections • Mucus in faeces • In heavy parasitemia • Anaemia • Hemorrhoids can result from continuous irritation of the bowel with resultant weakness of the levatorani muscle • Incraesed white blood cell count • Abdominal pain and tenderness • Vomiting and weight loss

9. TRICHURIASIS (contd) • DIAGNOSIS • Same as for Ascariasis • TREATMENT • Mebendazole and Albendazole are drugs of choice • Iron supplements if anaemia • PREVENTION AND CONTOL • Same as for Ascariasis

10. ENTEROBIASIS • AKA Pinworm • Caused by Enterobiusvermicularis • Has the widest geographical distribution of the helminthes (nematodes) • More common in children • Higher incidence in whites than blacks • It is the most common worm infection in the USA • Man is the only host

11. ENTEROBIASIS (contd) • LIFE CYCLE • Infection can be by ingestion of the worms directly or indirectly • After ingesting the eggs, larva hatch in the duodenum • The adult gravid female matures in the small intestine and migrates to the colon where it lays eggs in the anus at night, while the host is asleep • The eggs can then be easily be transferred from the hand to the mouth • The eggs survive for 2-3 weeks in the indoor environment- e.g. on toys, beddings, toilet seat.

12. ENTEROBIASIS (contd) • CLINICAL FEATURES • The most common presentation is pruritus ani • This can lead to secondary infection from repeated scratching • The pruritus and discomfort can lead to secondary reflex symptoms of insomnia, abdominal pain and grinding of teeth • They can be found in the appendix and cause appendicitis • DIAGNOSIS • Looking for worms in the peri-anal region 2-3 hours after the infected person is asleep • Can also be by using Graham’s Scotch adhesive tape swab in younger children, in the morning, and the tape viewed under a microscope

13. ENTEROBIASIS (contd) • TREATMENT • Mebendazole, Albendazole and Pyrantelpamoate. 1st dose is given and another dose repeated 2 weeks after. 2nd dose is to help eliminate re-infection • It is advisable that all household should be treated at the same time • PREVENTION AND CONTROL • Good personal hygiene especially hand washing, avoid biting nails (nails should be cut) • Health education • Proper faeces disposal • Infected people should not bath with others so water is not contaminated

14. VISCERAL LARVA MIGRANS • More common in preschool aged children where they are prone to eating dirt • Associated with Ascarid larva of dogs and cats, chiefly of Toxocaracanis • Lesions have been found in the liver, brain and lungs • CLINICAL FEATURES • Persistent eosinophilia • Hepatomegaly • Seizures • Encephalitis • Myocarditis • Lung involvement- fever, cough • Ocular involvement can lead to visual loss

15. VISCERAL LARVA MIGRANS (contd) • DIAGNOSIS • Stool culture to rule out other infections • Serology using Enzyme linked immunosorbent assay (ELISA) is commonly used for diagnosis • TREATMENT • This is aimed at symptom relief- using vitamins, Iron supplements, antibiotics, steroids and antihistamines for inflammation • Antihelminthics- Mebendazole • Treatment of infected cats and dogs with antihelminthics

16. CUTANEOUS LARVA MIGRANS • It is a roundworm infection (usually hookworms) • Found under the skin • Caused by larval stages of dog and cat hookworms (Ancylostomaspp) • Infection occurs when contaminated soil comes in contact with the skin. Can also be gotten from beach sand • Fecal matter that contain the eggs are shed by the infected host into the soil where they develop into larva. These larva then penetrate the skin and migrate through the epidermis • There is worldwide distribution of dog tapeworm which is more commonly associated with CLM • More in tropical regions where warmth and moisture are conducive for development of the larva in the soil

17. CUTANEOUS LARVA MIGRANS (contd) • CLINICAL FEATURES • Characterized by erythematous track that appear on the skin • Itching which is worse at night • Swelling • More commonly found in the feet and buttocks • Infection may heal spontaneously but secondary bacterial infection can also result • DIAGNOSIS • Mainly by characterizing the skin lesions • There may or may not be eosinophilia

18. CUTANEOUS LARVA MIGRANS (contd) • TREATMENT • Albendazole is the treatment of choice • PREVENTION AND CONTROL • Health education • Wearing shoes and protective clothing when in the sand or beach • Not sitting directly on the sand

19. REFERENCES • Centers for Disease Control and Prevention (2013). Parasites- Ascariasis; http://www.cdc.gov/parasites/ascariasis/ • Centers for Disease Control and Prevention (2013). Parasites- Trichuriasis (also known as Whipworm infection); http://www.cdc.gov/parasites/whipworm/ • Centers for Disease Control and Prevention (2013). Parasites- Enterobiasis (also known as Pinworm infection); http://www.cdc.gov/parasites/pinworm/ • Centers for Disease Control and Prevention (2013). Cutaneous Larva Migrans;http://wwwnc.cdc.gov/travel/yellowbook/2012/chapter-3-infectious-diseases-related-to-travel/cutaneous-larva-migrans.htm • Dold, C. and Holland, C.V. (2010). Ascaris and Ascariasis, Microbes and Infections; DOI 10.1016/j.micinf.2010.09.012 • Medscapereference (2013). Visceral Larva Migrans; http://emedicine.medscape.com/article/1000527-overview