1 |

Deworming and immunization

synergies and opportunities

Deworming and immunization

synergies and opportunities

Antonio MontresorNeglected Tropical DiseasesPreventive Chemotherapy and Transmission Control

2 |

- Health damages of worm infections and the benefit of deworming

Presentation Outline

- Advantages of including deworming in vaccination and vitamin A distribution programmes

- Brief introduction about worms

3 |

Main worms in childrenMain worms in children

Ascaris lumbricoides (roundworms)

Trichuris trichiura (whipworms)

Ancylostoma duodenale and

Necator americanus (hookworms)

The adult worms measure between 1 cm (hookworm) to 20 cm (roundworms).

Worm infections are the most widespread infections worldwide

(>2 billion people)

4 |

Worm cycleWorm cycle

Worms do not reproduce in the human body but produce eggs that are contaminating the environment and infecting other persons

Children are particularly susceptible to worm infections.

5 |

Individuals in a period of intense physical and intellectual

growth are particularly at risk

Individuals in a period of intense physical and intellectual

growth are particularly at risk

Foetal

0 1 2 3 4 5 10 15 20 40 60

Infant Preschool age School-age Reproductive age

A. lumbricoides - REDUCED GROWTH RATE

T. trichiura - reduced growth rate - iron deficiency COGNITION DEFICIT

Hookworm IRON DEFICIENCY - ANAEMIA

Crompton and Nesheim Annu Rev Nutr 2002 35-59

The dose of anthelminthic is the same for all age groups (1 tablet)

except for the children between 1 and 2 years (1/2 tablet)

6 |

We can recognize an infected child by examining microscopically the stool for the presence of worm eggs

7 |

We can recognize an infected child by examining microscopically the stool for the presence of worm eggs

A child can be infected by few worms and will have few worm eggs by gram of faeces, or by several worms and will have several thousands of eggs by gram of faeces

8 |

Treatment intervalsTreatment intervals

Individual diagnosis is much more expensive than treatment.

WHO recommends to treat all the children when a survey show that more than 20% of the children in that area is infected.

If the prevalence is over 50%, two treatments a year are recommended

9 |

Which are the health damages

caused by worms?

10 |

Worm infections cause blood lossWorm infections cause blood loss

0000

2222

4444

6666

8888

10101010

12121212

intensity of hookworm infection (epg)

0 <2000 <4000 <6000 <8000 >8000

Intensity of hookwom infection (eggs per gram)

Faecal

occu

lt b

loo

d

(mg

blo

od

/g fa

eces)

Stoltzfus 1996 Am J Trop Med Hyg 55 399-404

For example

In Vietnam 85% of children are infected by worm, 20% of which with heavy infection.(Montresor et al 2004)

In large areas of Tanzania 95%of the children is

infected by worms, 25% of which with heavy infection. (Albonico et al 1997)l

In several large areas of Bolivia over 75% of the

children is infected.(MoH 2008)

11 |

Worm infections are associated

with anaemia

Worm infections are associated

with anaemia

Intensity of hookwom infection

Pre

vale

nce o

f A

naem

ia

0

10

20

30

40

50

No inf Low Moderate High

Yip, R., 1996 UNICEF, Viet Nam

12 |

Weight gainWeight gain

The provision of periodic anthelminthictreatment as a part of child health services in Uganda resulted in an increase in weight gain of about 10% (166 g per child per year) above the expected weight gain.

Alderman et al BMJ 2006

13 |

Control worm infection can result in an increase of the haemoglobin of 2 g/dl

Control worm infection can result in an increase of the haemoglobin of 2 g/dl

Mean Hb for cohort participants

10.00

11.00

12.00

13.00

14.00

Baseline

(n=202)

Survey 1

(n=153)

Survey 2

(n=202)

Mean

Hb All follow-ups

Baseline Hb >= 12

Baseline Hb < 12

14 |

5.45.45.45.4

5.65.65.65.6

5.85.85.85.8

6666

6.26.26.26.2

6.46.46.46.4

6.66.66.66.6

6.86.86.86.8

7777

7.27.27.27.2

7.47.47.47.4

20202020

21212121

22222222

23232323

24242424

25252525

T

T

Uninfected (control)

Worm infections affect language and memory development

Nokes et al (1992) Parasitology 104 539-547

Treated (albendazole)

Infected (placebo)

Memory test Fluency test

Beginning of the school year

Beginning of the school year

End of the school year

End of the school year

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Lesson from the veterinary field Lesson from the veterinary field

These animals are of the same specie, sex and age

Periodicallydewormed

Not receiving

deworming

16 |

QUIZ:How much cost a tablet

of albendazole?

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A- 2 USD (With 10 USD we can deworm 5 children)

B- 0.2 USD (With 10 USD we can deworm 50 children)

C- 0.02 USD (With 10 USD we can deworm 500 children)

D- 0.002 USD (With 10 USD we can deworm 5000 children)

18 |

SafetySafety

The deworming tablet is practically not absorbed by the intestine.

99.5% of the tablet remains in the intestinal lumen, where reaches and kills the worms.

Some "discomfort" could be filled by the child but is due to the dying worms

19 |

Which are the additional advantages

of deworming?

20 |

Synergy with other programmesSynergy with other programmes

The combination of different interventions increases the health benefits at marginal cost

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Deworming is popular and can increase programme coverage

Deworming is popular and can increase programme coverage

Frequently, expelled worms are observed in the child faeces by the mother in the day following deworming.

This reinforce the trust in the health services

22 |

Deworming increases vitamin A

absorption

Deworming increases vitamin A

absorption

Mahalanabis et al (1976) Am J Clin Nut 29 1372-1375

Possible mechanisms involved:• worms in the intestine

compete for vitamin A rich food

• worm induce malabsorption(reduction of the capacity to absorb vitamin A of the intestine)Absorption before

treatment

Absorption after

treatment

23 |

Animal and human studies suggested that worm infection has an impact on immunity

Animal and human studies suggested that worm infection has an impact on immunity

Urban et al Vet Parasitol 2008 148 14-20Borkov, Trends in Parasitology 2008 24 243-45Elias et al Clin Exp Immunol. 2001 123: 219–225.

Pigs infected with Ascaris suum present reduced immune-response to vaccine for pneumonia

Mice infected with worms respond less efficiently to vaccinationduring tests of the malaria vaccine

Tuberculin reaction after BCG is more evident in individuals receiving deworming at vaccination

24 |

Immunity and WormsImmunity and Worms

Suggested explanation

To ensure their survival in the host for years, worms induces particular immuno-modulatory and –regulatory mechanisms in the host’s immune system:

- Immune activation - Biased Th2 response - Down regulation of Th1 and CTL activity.

These changes impair the immunological response to pathogens andvaccines.

Kamal, parasite immunology 2006

25 |

Administration of deworming is very simple

Administration of deworming is very simple

Cold chain

Sterilization of equipment

Training of personnel

The administration of a single tablet of albendazole to each child presenting for vaccination or vitamin A supplement is so simple, that a simple printed page is normally sufficient to explain the procedure to the staff

26 |

PrecautionsPrecautions

Only two precautions should be taken by the health workers:

1- do not force any child that is refusing the tablet

2- crash the tablet before administering it to small children (from 1 to 2 year of age)

27 |

ConclusionsConclusions

� Deworming has significant health impact

� Deworming is cheap

� Deworming is simple

� Deworming is safe

� Deworming is synergic with immunization and vitamin A distribution campaigns

� Deworming improve increase immunization and vitamin A distribution campaigns coverage

28 |

Countries where intestinal helminths are a public health problem

Countries where intestinal helminths are transmitted

Worm are intensely transmitted in almost all the tropical and sub tropical countries

29 |

WHO can provide a detailed epidemiological situation of worms for almost all the endemic

countries

WHO can provide a detailed epidemiological situation of worms for almost all the endemic

countries

30 |

Documents & publications (I)Documents & publications (I)

Helminth control strategy

Inclusion of deworming into existing delivery channels

31 |

WHO offers technical support to all Vaccination or vitamin A programmes intending to include

deworming

WHO offers technical support to all Vaccination or vitamin A programmes intending to include

deworming

WHO Contacts

HQ: Antonio Montresor <montresora@who.int >

AFRO: Mubila Likezo mobilal@zw.afro.who.int>

PAHO: Steven Ault <aultstev@paho.org>

SEARO Chusak Prasittisuk <chusakp@searo.who.int>

WPRO: John Ehrenberg <ehrenbergj@wpro.who.int>

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Please visit our websitesPlease visit our websites

� The WHO Department of Control of Neglected Tropical Diseases:

http://www.who.int/neglected_diseases/en/

� For documents and publications:

http://www.who.int/wormcontrol/documents/en/

� For the newsletter "Action against Worms": http://www.who.int/neglected_diseases/preventive_chemotherapy/pctnewsletter/en/index.html