Diseases are spread through several means including infected body fluids such as blood, faeces, vomit, saliva and nasal secretions. Pathogenic objects include microorganisms, poisons, pollutants etc. transmission (i.e. invasion of fluid) may be direct or through several vehicles such as air, insects (vectors) or intermediate hosts (mollusks and lower vertebrates).
To control disease, it is important to identify the pathogen involved, the vehicle used and the fluid affected.
Reduction in disease level may be achieved through preventive (preventing disease transmission) or morbidity control (reducing the effect of established disease on individuals and communities).
Preventive measures are aimed at preventing pathogens from gaining access to the body fluids while control methods involved reducing or eliminating pathogens in the body fluids. The specific methods used to achieve these are outlined below.
Preventive Methods
The preventive methods involve taking precautionary measures to prevent pathogens and pollutants reaching the body fluids. It also includes activities carried out to reduce vector and intermediate host population.
Methods to prevent infection and injuries can be directed either to host or environment and include:
Standard Precautions
Hand Hygiene – The most important hand hygiene method is to wash hands for at least 20 seconds, using soap and warm running water before handling food or eating, after using the bathroom and toilet, diapering, handling raw meat, cleaning activities, making contact with pets, patients and after any activity that contaminates the hands.
Children and infants need help to wash their hands properly.
Use of personal protective equipment (PPE): gloves, aprons, eye protection, face masks etc.
Handle and dispose of sharps objects safely
Dispose of contaminated waste safely
Managing blood and body fluids: spillages and transport of specimens
Decontaminating equipment: cleaning, disinfection and sterilization
Maintain a clean clinical environment
Prevent occupational exposure to infection
Manage sharp injuries & blood splash incidents
Manage linen safely
Place patients with infections in appropriate accommodation
Correct disposal of excretions & soiled material
Soiled clothing & bed linen – place in a hot wash (>60)
Disinfection is especially important in nurseries, schools & residential institutions
Health education should emphasize personal hygiene & hygienic preparation and serving of food
Parasite Targeted Control
Three major methods are used to reduce parasite load in infectious diseases, either in animals or plants.
The first is to destroy any animal infected by the parasite organisms, whether it be the host animal or an intermediate host, such as an insect or mollusks that transmit the infective organism.
This method, however, cannot be used in the human population even when it works very effectively in other animal populations.
Typical examples are the eradication in the United States of hog cholera in swine and yellow fever in humans through the elimination of hog and mosquitoes respectively.
The second method is therapeutic using synthetic and herbal drugs including antimicrobial drugs.
The development of resistant strains of many micro-organisms to a number of antimicrobial drugs and high rate of re-infection has limited the efficacy of these methods and caused concern although the method is still widely used.
A third method of control is to immunise with a form of the organism that will induce an immune response. This requires the use of vaccines containing an immunogen that induces persisting protection against the invading organism. This method offers the greatest promise.
It is simple, inexpensive, requires few administrations, and, most importantly, prevents infection and, therefore, minimises damage that often accompanies infection. Greater safety and effectiveness in newer biological products will enhance their use.
Immunisation exposes individuals to infectious agents artificially so that they will develop antibodies and be protected against the common disease-causing organisms. The vaccines in common use are made from either attenuated living organisms or inactivated organisms.
The attenuated living organisms have reduced virulence, are required only in small amounts, and, in general, induce long-lasting immunity. They elicit a controlled subclinical infection and, in general, are very effective.
Occasionally, however, they produce side effects that may be as severe as the natural infection. Inactivated vaccines are safe in that they do not contain any infectious material, but they are weak in terms of stimulating an immune response.
They usually require multiple injections over several weeks to induce an immune response comparable to that induced by living organisms. They also may cause undesirable side effects evident both at the site of inoculation and sometimes as a general side reaction as the individual responds adversely to the many antigenic components in the vaccine.
In other words, the use of whole organisms in either the living or inactivated form may cause adverse reactions. These reactions are due to certain components of the whole organism, that is, proteins, lipids or carbohydrates that may not be necessary for immunisation. Biotechnology is improving this lapse as we will see later.
Vector Control Methods
Integrated vector control method is a holistic approach to managing vector populations and is based on the understanding of the interrelationship between the vector, the environment and humans.
Such understanding leads to the selection and deployment of the most cost- effective and sustainable intervention(s), either individually or combined – the objective being to achieve the maximum possible reduction or local elimination of the disease transmitting vectors and intermediate hosts.
The table below summarizes the common interventions currently used for the vectors of major human diseases.
| Table of chemical-based and non-chemical vector control methods(Source:IVM, 2012) | |||
| Control Method | Brief Description | Disease Targets | Major Vectors Targeted |
Chemically-based vector control method | |||
| Adulticides | |||
| Indoor residual spraying | Timely application of long-lasting chemical insecticides on the walls and ceilings of houses in order to kill the adult vectors that land on these surfaces. | Malaria, lymphatic filariasis, visceral leishmaniasis (kala-azar), chagas disease. | Indoor biting/resting female Anopheles mosquitoes; phelbotomine sandflies; reduviid bugs |
| from disease- baring insects. | |||
| Other I nsecticide- impregnated materials | Use of insecticide- impregnated clothing, coverings (blankets), door and window blinds, etc to prevent human-vector contact and bites | Malaria, lymphatic filariasis, cutaneous leishmaniasis, African trypanosomiasi s (sleeping sickness), onchocerciasis | Anopheles, Aedes, Culex mosquitoes; phelbotomine sandflies; tsetse flies; Simulium damnosum black flies |
| Molluscicid es | The use of molluscicides and insecticides to kill disease vectors in the adult stages. | Schistosomiasi s, lymphatic filariasis, dengue | Fresh-water snails (Biomphilaria, Bulinus, Onchomelania); Anopheles, Aedes, Culex mosquitoes |
| Insect Traps | Insecticide- impregnated traps targeting flying vectors; may also have an attractant (color or light) | Malaria, African trypanosomiasi s (sleeping sickness) | Anopheles, Aedes, Culex mosquitoes; tsetse flies |
| Chemical larvicides | The release of chemicals on water bodies and surfaces to kill larvae and pupae of insect vectors. | Malaria, dengue, lymphatic filariasis, onchocerciasis | Anopheles, Aedes, Culex mosquitoes; Simulium damnosum black flies |
Non-ChemicalVector Control Methods Non- Chemically- based control methodsEnvironmentalmethods | |||
| elimination of local vector breeding areas | schistosomiasis | Bulinus, Onchomelania) | |
| Manipulatio n | Temporary environmental changes to disrupt the reproductive cycle of a vector | Malaria, dengue, lymphatic filariasis, schistosomiasis | Anopheles, Aedes, Culex mosquitoes; Fresh-water snails (Biomphilaria,Bulinu s, Onchomelania) |
| House Modification | An improvement in the housing structure to restrict entry of disease vectors | Malaria, lymphatic filariasis, Chagas diseases | Indoor biting/resting female Anopheles mosquitoes; reduviid bugs |
Larviciding | |||
| Larvivorous fish | Use of natural predators (tilapia and other fish) that feed on the larvae and pupae of mosquito vectors | Lymphatic filariasis | Anopheles, Aedes, Culex mosquitoes; |
| Biological larviciding | The use of bacteria against mosquito larvae or pupae (e.g. Baccillus thuringiensis) | Malaria, dengue, lymphatic filariasis, onchocerciasis | Anopheles, Aedes, Culex mosquitoes; Simulium damnosum black flies |
| Non-larvivorous natural predators | The use of natural predators against disease vectors (e.g. molluscivorou s fish, Crawfish and crabs) | Schistosomiasi | Fresh-water snails (Biomphilaria, Bulinus, Onchomelania); |
| Polystyrenebeads | Formation of a layer on top of the breeding water body to prevent the larvae and pupae from breathing | Malaria, dengue, Lymphatic filariasis | Mosquitoes |
| Others | |||
| TopicalRepellants | Use of topical insecticides to repel biting insect vectors as a personal protection measure. | Malaria, dengue, lymphatic filariasis, African trypanosomiasi s (sleeping sickness) | Mosquitoes; tsetse flies |
In summary, waste management methods are both traditional and modern. The traditional methods include those methods that are used by households, municipal agencies and institutions, offices, etc. on daily bases including indiscriminate dumping and open burning, composting, sanitary landfill and incineration.
Read Also : The Two (2) Main Modern Waste Management
The modern methods target waste management form source, recycling those that are still useful in other sectors of the economy and developing technologies to minimise the quantity of waste produced by each activity.
Several methods used in pest and disease control were also described. These included appropriate personal hygiene, chemical and non-chemical methods of vector control.
The traditional methods involve collection and disposal without prior consideration of the environmental consequences. These methods include indiscriminate dumping and open burning, composting, sanitary landfills and incineration.
On the other hand, the modern methods such as recycling and source reduction technologies make environmental consequences a critical outcome of management, for which reason they are source based, considering not just collection and disposal, but also how the wastes are generated.