Protection of foods

Food-transmitted infections can spread either through contamination or by a specific intermediate host. Flies indirectly contaminate food. Protection of the food we eat can be by the following:

Excreta Borne Dsease
Fig. 3.4. Routes of transmission of the water- and sanitation-related diseases.
Table 3.1. A classification of water- and excreta-related diseases.

Category

Characteristics

Examples

Transmission

Control measures

1.

Water-

Diseases of poor

Skin diseases, eye

Person-to-person

Personal hygiene

washed

hygiene

diseases, louse-

(and

Increase water

disease

borne typhus

autoinfection)

quantity

2.

Faecal-oral

(a) Low infective

Enterobius,

Person-to-person

Personal hygiene

diseases

dose

amoebiasis,

(and

Increase water

enteric viruses

autoinfection)

quantity

(b) High infective

Diarrhoeal diseases,

Contamination of

Excreta disposal

dose. Able to

cholera, typhoid,

food or water

Cook food

multiply

hepatitis A

Improve water

outside host

quality

3.

Soil-mediated

(a) Development

Ascaris, hookworm,

Larvae penetrate

Personal hygiene

diseases

in soil

Strongyloides

skin or swallowed

Excreta disposal

(helminths)

(b) Development

Taenia spp.

Cysts in meat

Meat inspection

in animal

Cook food

(cow or pig)

intermediate

host

4.

Water-based

Helminths

diseases

requiring

intermediate

hosts

(a) Copepods

Guinea worm

Ingested in water

Improve water

quality

(b) Snails only

Schistosomiasis

Penetrates skin

Reduce water

contact

(c) Two

Fasciolopsis,

Eating uncooked

Excreta disposal

intermediate

Opisthorchis,

specific foods

Cook food

hosts

Paragonimus,

Diphyllobothrium

5.

Water- and

(a) Breeding in

Malaria, filariasis,

Mosquitoes

Drain breeding sites

excreta-

water or

arboviruses

Maintain water

related insect

sewage

supplies and

vectors

sanitation

(b) Breeding or

Onchocerciasis,

Simulium

Water supply at site

biting near

trypanosomiasis

Tsetse fly

of use

water

(c) Breeding in

Diarrhoeal diseases

Housefly

Excreta disposal

excreta

Modified from Bradley, D.J. (1978) In: Feachem, R.G. etal. (eds) Water, Wastes and Health in Hot Climates. Reproduced by permission of John Wiley & Sons Ltd, Chichester.

Modified from Bradley, D.J. (1978) In: Feachem, R.G. etal. (eds) Water, Wastes and Health in Hot Climates. Reproduced by permission of John Wiley & Sons Ltd, Chichester.

• inspection of raw produce;

• packaging and avoiding contamination;

• suitable storage conditions and timelimits;

• washing and correct preparation;

• adequate and even cooking;

• preventing contamination of cooked foods;

• eating cooked foods immediately.

Infections that can be reduced by the proper protection of food are shown in Table 3.4.

Table 3.2. The potential impact of environmental control methods (compare with Table 3.1).

Disease category

Personal hygiene

Cooking of foods

Water supplies

Sanitation

Miscellaneous

1.

Water-washed diseases

+ + +

_

++

+

_

2.

Faecal-oral diseases

+ + +

+

++

+

-

3.

Soil-mediated diseases

++

+ + +

-

+ + +

Meat inspection

4.

Water-based diseases

-

+ + +

++

+

Reduce water contact

5.

Water- and excreta-

-

-

Protection from insects

related insect vectors

+ + +, Very effective; ++, moderately effective; +, effective; -, not effective; ±, can be either effective or not effective.

+ + +, Very effective; ++, moderately effective; +, effective; -, not effective; ±, can be either effective or not effective.

Table 3.3. Infections that can be reduced by personal hygiene.

Category Infection

1 Skin sepsis and ulcers

1 Conjunctivitis

1 Trachoma

1 Scabies

1 Yaws

1 Leprosy

1 Tinea

1 Louse-borne fevers

1 Flea-borne infections (including plague)

2 Enteric viruses (including hepatitis A and polio)

2 Enterobius

2 Amoebiasis

2 Trichuris

2 Giardia

2 Shigella

2 Typhoid

2 Other Salmonellae

2 Campylobacter

2 Non-specific diarrhoeal diseases

2 Cholera

2 Leptospirosis

3a Ascaris

Category 2 infections contaminate food before or after cooking. Flies are often involved. Even if contamination has occurred, correct storage and the disposal of cooked foods after a limited time can prevent sufficient multiplication of bacteria to reach an infective dose.

Categories 3b and 4c (Table 3.4) require specific intermediate hosts in their transmission, so their destruction or proper cooking is an effective means of control. Cooking needs to be at a sufficiently high temperature to kill off the intermediate stages and procedures, such as roasting on a spit or cooking meat 'under done', do not provide high enough temperatures inside the meat. Meat inspection can be effective in Taenia infection (3b).

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