Dr. Igbinedion

MBBS, MPH, FRSPH, ACIEH

EPIDEMIOLOGY AND CONTROL OF HELMINTHIC

INFESTATION (contd.)

AKA BilharziasisCaused by Schistosoma spp.- mansoni,

haematobium, japonicum, intercalatum and mekongi- which affect humans

It is a parasitic infectionSnails are the intermediary agents between

hostsInfection is by consuming water contaminated

by infected snailsCommonly found in Asia, Africa and South

America

Schistosomiasis

Affects children more than adultsSecond most devastating parasitic disease

socioeconomically, after malariaInfection is gotten when individuals-

particularly children- come in contact with contaminated water, either by playing or swimming

The parasitic larva then penetrate the skin and mature within the organs

Schistosomiasis (contd.)

Life cycle- Snail and Man

Schistosomiasis (contd.)

Signs and Symptoms- acute or chronic (acute- occurs within a few weeks of infection)

abdominal paindiarrheaeosinophilia hepatosplenomegalyesophageal varicesskin symptoms- itching and dermatitisCNS involvementBladder cancer

Schistosomiasis (contd.)

DiagnosisDetection using ELISA- highly effectiveStool and urine microscopy

PreventionEliminate snails that dwell in the water

using acrolein, copper sulfate or niclosamideAvoiding the snails

TreatmentPraziquantel

Schistosomiasis (contd.)

Caused by Strongyloides stercoralis, a roundworm

More common in tropics and warm temperate regions

Infection is through contact with soil contaminated by Strongyloides larvae

Low socioeconomic factors and institutionalized populations are risk factors

Strongyloidiasis

Strongyloidiasis (contd.)

Clinical FeaturesMostly asymptomaticAbdominal painBloating, heartburnDiarrhea, constipationNauseaLoss of appetiteCoughItchy, red rash

Strongyloidiasis (contd.)

DiagnosisStool microscopy

TreatmentIvermectin- drug of choiceThiabendazoleAlbendazole

Strongyloidiasis (contd.)

Prevention and controlWear shoesGood hygieneProper sewage disposal

Strongyloidiasis (contd.)

Causes lymphatic filariasisCaused by Wuchereria bancrofti- most common

worldwide; In Asia- Brugia malayi and Brugia timori

Nematode (roundworm)More common in tropical and sub tropical areasInfection is spread through mosquito bites from

person to personMosquitoes involved- in Africa, Anopheles

mosquitoes; in the Americas, Culex quinquefasciatus; in the Pacific and Asia, Aedes and Mansonia

Filariasis

LIFECYCLE OF Wuchereria bancrofti

Lifecycle of Brugia malayi

Clinical FeaturesUsually asymptomaticLymphedema in a small percentage of

patients- legs, arms, breast, genitaliaElephantiasis- hardened and thick- ened skin from bacterial infectionHydrocele or scrotal swelling- W. bancrofti

Filariasis (contd.)

Diagnosis Identifying microfilaria in the blood using

microscopy. Blood sample should be taken at night because that is when the microfilaria circulate

Serology

TreatmentDiethylcarbamazine (DEC)For lymphedema, there is no active filarial infection

so DEC is not indicated- Refer to lymphedema therapist for education on hygiene and exercise

Surgery for hydrocele

Filariasis (contd.)

Prevention and control

Avoid mosquito bites- within dusk and dawn, when they bite

Protective clothingMosquito repellantMosquito nets

Filariasis (contd.)

Caused by Loa loaNematode (roundworm) in the Lymphatics

and subcutaneous tissuesAKA African eye wormTransmitted through repeated bites of

deerflies which breed in muddy, shaded areas along rivers

Found in West and Central AfricaThe deerflies bite during the day and are

attracted by movement and smokeMore common in rainy season

Loaisis

Lifecycle Loa loa

Clinical FeaturesAsymptomaticCalabar swellings- local angioedema (non

tender found on limbs and near joints); associated with itching

Eye worm- itching, pain photophobia. Usually lasts hours and does not damage the eye

Generalized itchingMuscle and joint painFatigue

Loiasis (contd.)

Diagnosis Identifying the adult worm in the eye Identifying larvae in the blood taken between

10am and 2pm Identifying the worm after removal from the body

TreatmentSurgical removal of migrating adult worm from

skin or eyeDEC- kills larvae and adult wormAlbendazole- kills adult worm

Loiasis (contd.)

Prevention and controlDEC weeklyAvoiding breeding sites and smokePersonal protection- protective clothing,

repellants

Loiasis (contd.)

AKA River BlindnessCaused by Onchocerca volvulusNematodes in the subcutaneous tissuesTransmission is through repeated bites of

Simulium blackflies which breeds near fast flowing rivers and streams and bite during the day

Found in the tropics especially sub Saharan Africa

Onchocerciasis

Onchocerca volvulus Lifecycle

Clinical featuresSoma are asymptomaticSkin rashes, itchySubcutaneous nodulesVisual changesLeopard skin appearance from long term

inflamed and itchy skinHanging groin- loss of skin elasticityBlindness- from inflammatory reaction of

dead larva in the eye

Onchocerciasis (contd.)

DiagnosisSkin snip from different parts of the bodyExamination of a surgically removed noduleEye examination

TreatmentIvermectinBefore administering medication, ensure there

is no Loa loa infection because it can cause severe side effects to medications for Onchocerciasis.

Onchocerciasis (contd.)

Prevention and control

Personal protective measures are the most important

Mass treatment with ivermectin

Onchocerciasis (contd.)

http://www.cdc.gov/parasites/schistosomiasis/http://www.cdc.gov/parasites/strongyloides/http://www.cdc.gov/parasites/lymphaticfilaria

sis/

http://www.cdc.gov/parasites/loiasis/http://www.cdc.gov/parasites/onchocerciasis/

index.html

References