5.1 Microbes and Worms
Some microorganisms are among organisms that are a health problem. These
organisms include certain bacteria, protozoa, fungi, and algae. Viruses and rickettsia
(acellular microbes) are also in this group since methods used to control them are
similar to those used for bacterial control. Recently, however, much concern has
been expressed over the inadequacy of detection methods to quantitatively determine infectious viruses. Researchers recognize that water deemed safe by the
coliform index may be virologically unsafe. Disinfection of water by chlorination
is the most common choice for the control of viruses, rickettsia, and infectious
bacteria such as the enterics and the various spirochetes responsible for leptospirosis.
Chlorination also is often used to control other water-borne pathogens such as the
protozoan Entameba histolytica as well.
Certain water-borne flatworms and round worms that infect humans are also
controlled by disinfection techniques. More commonly, however, since foods are
common vehicles of infection, proper cooking measures can control the spread of
these parasitic worms. A summary of food and water-borne diseases, along with
their etiological agents, prevention, and control, is given by Salvato [9].
Microorganisms that produce respiratory diseases are usually spread via the air or
by direct contact with an infected individual. These organisms are best controlled
through personal cleanliness of the infected individual. Other measures include
disinfecting aerosols and disinfection of surfaces upon which the pathogens fall.
Disinfection is likewise used to control fungi that produce various forms of skin
disease (dermatophytosis). People most commonly contract skin diseases of fungal
origin where conditions include moisture, warmth, and other people, such as swimming pools and shower rooms. Dermatophytosis is controlled at the source by
measures capable of killing the fungal spores. The simplest of these is the drying
of the infected area, which destroys both the vegetative fungi and the fungal spores.
Chemical means normally used are either disinfection with sodium hypochlorite
(500 mg/L available chlorine) or scrubbing the facility frequently with a hot solution
of strong detergent followed by a rinse with a disinfectant.
Health hazards originating from algae arise via their endotoxins, some of which
are highly poisonous to humans. Most noteworthy are shellfish contaminated by the
alga Gonyaulax. The control of algae will be discussed later in this chapter.
5.2 Arthropods
Arthropods affecting human health contain a wide class of organisms, most inclusive
of insects for purposes of this section. More people have died from malaria than the
combined deaths of World Wars I and II. The protozoan parasite is carried by
mosquitoes of various species in the genus Anopheles. In addition, mosquitoes
transmit dengue fever, encephalitis, filariasis, Rift Valley fever, and yellow fever,
10 Environmental Control of Pests and Vectors
397
Some microorganisms are among organisms that are a health problem. These
organisms include certain bacteria, protozoa, fungi, and algae. Viruses and rickettsia
(acellular microbes) are also in this group since methods used to control them are
similar to those used for bacterial control. Recently, however, much concern has
been expressed over the inadequacy of detection methods to quantitatively determine infectious viruses. Researchers recognize that water deemed safe by the
coliform index may be virologically unsafe. Disinfection of water by chlorination
is the most common choice for the control of viruses, rickettsia, and infectious
bacteria such as the enterics and the various spirochetes responsible for leptospirosis.
Chlorination also is often used to control other water-borne pathogens such as the
protozoan Entameba histolytica as well.
Certain water-borne flatworms and round worms that infect humans are also
controlled by disinfection techniques. More commonly, however, since foods are
common vehicles of infection, proper cooking measures can control the spread of
these parasitic worms. A summary of food and water-borne diseases, along with
their etiological agents, prevention, and control, is given by Salvato [9].
Microorganisms that produce respiratory diseases are usually spread via the air or
by direct contact with an infected individual. These organisms are best controlled
through personal cleanliness of the infected individual. Other measures include
disinfecting aerosols and disinfection of surfaces upon which the pathogens fall.
Disinfection is likewise used to control fungi that produce various forms of skin
disease (dermatophytosis). People most commonly contract skin diseases of fungal
origin where conditions include moisture, warmth, and other people, such as swimming pools and shower rooms. Dermatophytosis is controlled at the source by
measures capable of killing the fungal spores. The simplest of these is the drying
of the infected area, which destroys both the vegetative fungi and the fungal spores.
Chemical means normally used are either disinfection with sodium hypochlorite
(500 mg/L available chlorine) or scrubbing the facility frequently with a hot solution
of strong detergent followed by a rinse with a disinfectant.
Health hazards originating from algae arise via their endotoxins, some of which
are highly poisonous to humans. Most noteworthy are shellfish contaminated by the
alga Gonyaulax. The control of algae will be discussed later in this chapter.
5.2 Arthropods
Arthropods affecting human health contain a wide class of organisms, most inclusive
of insects for purposes of this section. More people have died from malaria than the
combined deaths of World Wars I and II. The protozoan parasite is carried by
mosquitoes of various species in the genus Anopheles. In addition, mosquitoes
transmit dengue fever, encephalitis, filariasis, Rift Valley fever, and yellow fever,
10 Environmental Control of Pests and Vectors
397