Selective Primary Health Care Research Articles

Selective primary health care: strategies for control of disease in the developing world. XIX. Giardiasis.

Giardia lamblia infects millions of individuals throughout the world. In developed countries it appears primarily in waterborne epidemics of diarrhea. In developing countries, it is endemic, but only a small proportion of those infected appear ill. This flagellate parasite infects the small intestine of its host and may cause malabsorption and malnutrition, particularly among infants and young children. Little is known about the extent of illness caused by this parasite because few epidemiologic studies have been done; diagnosis is difficult and Giardia carriers frequently are simultaneously infected with other pathogens. Control measures include intermittent treatment of those infected and improved water supply and sanitation. Efforts to control individual infection can only be successful on a temporary basis. The greatest progress in control should derive from efforts to develop an effective vaccine.

Selective primary health care: strategies for control of disease in the developing world. XVII. Pertussis and diphtheria.

Pertussis and diphtheria, bacterial infections responsible for significant childhood morbidity and mortality in the developing world, are potentially controllable by mass immunization. The incidence of pertussis has been dramatically reduced in many areas of the world over the past 25 years by the use of pertussis vaccine. The massive increase in incidence of clinical pertussis in Great Britain and other European nations occurring after publicity about vaccine reactogenicity precipitated a marked decrease in vaccine acceptance has documented the efficacy of the vaccine and the necessity of continued immunization. The issue of potential toxicity is, nevertheless, being addressed with the development of a cell-free, component pertussis vaccine. The use of diphtheria toxoid, directed at protecting recipients against the systemic effects of diphtheria toxin, has resulted in excellent control of the disease in the United States and elsewhere. Certainly the use of these two vaccines on a mass scale is the preferred approach to worldwide control, if not eradication, of these infectious diseases.

Selective primary health care: strategies for control of disease in the developing world. XVII. Hookworm infection and anemia.

Approximately one-quarter of the world's population is infected with either Ancylostoma duodenale or Necator americanus. Humans transmit the hookworm by fecal contamination of the soil. The eggs hatch and the larvae may survive several months in warm, damp soil. Humans are infected when the larvae penetrate the skin and migrate through the body to the intestines, where the median survival time of the hookworm is one year. The loss of red blood cells into the gut is proportional to the worm load. Symptoms result from iron deficiency anemia and protein loss caused by a heavy worm burden. The peak age-specific prevalence of infection occurs in adult life, but only a small proportion of those infected ever become symptomatic. Possible control measures include chemotherapy to reduce the intensity of infection and the transmission potential and sanitation.

Selective primary health care: strategies for control of disease in the developing world. XVI. Chagas' disease.

Despite much research, specific chemotherapy for Chagas' disease remains problematic, and prophylaxis by vaccination seems remote. A significant proportion of today's positive seroreactive patients will burden tomorrow's hospital services with persistent cardiac failure, arrhythmias requiring pacemaker implantation, and megasyndromes requiring corrective surgical procedures. Yet the control of transmission to humans in many endemic areas is feasible by programs of residual insecticide spraying and subsequent vigilance and, in some instances, house improvement, i.e., measures to combat domiciliated vector bugs. The success of such programs will vary, depending on the dominant bug vector and degree of development of the country's public health services. The fact that the Brazilian government voted a large sum of money in 1983 for bug control by the Ministry of Health enforces this view. Transmission of Trypanosoma cruzi to humans could decrease considerably in the next decade in Brazil as a result of this program. There is, however, still a need for research to define the cheapest ways of interrupting transmission in different epidemiologic situations so that the maximum number of people at risk can be reached with the funds available, for the children infected today may be hospital patients of the future for whom little can be done.

Selective primary health care: strategies for control of disease in the developing world. XV. Acute diarrhea.

Diarrhea claims the lives of at least five million children per year and is a major contributor to malnutrition in developing countries. A variety of infectious agents cause diarrhea through several pathogenic mechanisms. Bacteria such as Shigella can directly invade the intestinal mucosa, and those similar to Vibrio cholerae or enterotoxigenic Escherichia coli can produce toxins that alter cellular absorption and secretions. Rotavirus appears to cause 30%–40% of diarrhea in toddlers. Diarrhea frequently accompanies parasitic infestation and infections in other parts of the body. Several methods, including improvement of water supplies and sanitation and administration of vaccines and antibiotics, may be useful in preventing mortality and morbidity due to diarrhea. Oral rehydration to replace fluids and electrolytes, accompanied by attention to early feeding and encouragement of breast feeding, is the most effective and economical intervention currently available.

Selective primary health care: strategies for control of disease in the developing world. XIV. Leishmaniasis.

The epidemiology of human leishmaniasis is most complex. Not only are there many species of the parasite in the tropics and subtropics, but each has different sand fly vectors and animal reservoirs and exhibits different behavior in humans. Where epidemiologic information is sufficient, one or more of four methods of control has been effectively used. These are spraying of houses with DDT to control domiciliated phlebotomines (southern Europe, India, Brazil), destruction of animal reservoirs (Brazil, USSR), mass treatment of patients (India, China), and vaccination (USSR, Israel). A drug replacing the pentavalent antimonials as the first-line treatment is a priority, since human infections resistant to currently available drugs occur in many countries and antimonials are difficult to give to outpatients. More research is needed on forest leishmaniasis in the tropical Americas; however, sand fly vectors and animal reservoirs seem inaccessible to control measures. If a vaccine can be developed, it might have great utility. There is an urgent need to map the distribution of predominant species infecting humans in Latin America, since treatment schedules differ for the various cutaneous infections.

Water supply and health in developing countries: selective primary health care revisited.

The inclusion of water supply and sanitation programs as a component of primary health care (PHC) has been questioned on the basis of calculations of the costs of these programs per infant death averted. In this paper the procedures used in these cost-effectiveness calculations are examined and found to be wanting. The calculations are misleading since gross rather than net costs have been used, and the health impact of these programs underestimated. It is also shown that the methodology used is biased against water supply and sanitation and other programs with multiple outputs. The time constraints facing mothers in implementing PHC programs, as well as the contribution of improved water supplies in alleviating these constraints are outlined. Data are presented to show that, if poor women in developing countries were to choose the mix of activities to be included in PHC programs, improved water supplies would frequently constitute part of that mix.

Selective primary health care: strategies for control of disease in the developing world. XII. Ascariasis and trichuriasis.

Ascariasis and trichuriasis are the most prevalent and widespread intestinal helminthiases. Transmission of disease occurs by ingestion or inhalation of Ascaris and Trichuris eggs embryonated in the soil. During the migration of Ascaris to the lungs, pneumonic symptoms may develop. The intestinal stage of the parasite can cause severe symptoms and complications when the worm burden is high. High numbers of Trichuris may cause diarrhea. The poor standard of hygiene, the biology of the parasite (which is such that a high number of very resistant eggs are produced), and the habits of the host (such as the use of night soil) are factors causing a high prevalence of infection in many countries in Asia, Africa, South America, and Europe. The mechanism of the transmission of Ascaris varies in different communities. The peak of infection is among children aged four to 14 years. Worm burden is normally low, and only a small segment of the population harbors a high proportion of the worms present in a community. Control of infections due to Ascaris and Trichuris is feasible by a combination of mass chemotherapy with the effective drugs now available, safe disposal of excreta, destruction of the eggs, and health education.

Selective primary health care: strategies for control of disease in the developing world. XI. Dengue.

Since World War II, dengue viruses have progressively extended their geographic domain and have increased as causes of human morbidity and mortality. This complex of four flaviviruses is principally transmitted to humans by the bite of Aedes aegypti, the yellow fever vector. Factors that promote the indoor storage of water are congenial to the breeding of A. aegypti. These include the dislocations of wars, overpopulation , and urbanization. By the mid-20th century, A. aegypti eradication campaigns had nearly succeeded in much of the Western Hemisphere. Since then, there has been a steady degradation in ability to cope with this species despite the fact that a newly emerged, severe immunopathologic disorder, dengue hemorrhagic fever/dengue shock syndrome, endows dengue epidemics with grave consequences. Development of a vaccine against dengue is complicated by the need to develop four different live attenuated vaccines and by a justifiable caution imposed by dengue immunopathology. A wide range of proven methods have been and are available to reduce populations of A. aegypti. This paper argues that the eradication strategy adopted earlier in this century is still viable and cost effective. Critical to a successful control program is a prioritied approach, a thorough, disciplined planning effort, a commitment to assessment, adequate compensation of staff, and, above all, the will to succeed.

Selective primary health care: strategies for control of disease in the developing world. X. Amebiasis.

The human parasite Entamoeba histolytica has a worldwide distribution. The majority of infected individuals suffer few symptoms; nonetheless, a variable proportion experience dysentery, hepatic abscesses, or invasion of other extraintestinal organs. Invasive amebiasis is a major health problem, particularly in certain developing countries. The aim of this review is to clarify, as much as possible, controversial issues about the biology of the parasite, the clinical features of amebiasis, and the estimations of morbidity and mortality rate as the basis for defining strategies for control of amebiasis by primary health care workers. The eradication of invasive amebiasis lies basically in potentially political and economic actions at the governmental level. Preventive and control measures include (1) provision of water supplies and sanitation, (2) health education, (3) adequate diagnosis and correct treatment of invasive amebiasis, and (4) implementation of surveillance and control programs.

Selective primary health care: strategies for control of disease in the developing world. VIII. African trypanosomiasis.

African trypanosomiasis in humans is caused by trypanosomes, parasitic protozoa that inhabit the blood and tissue spaces. Humans are infected by the bite of the tsetse (Glossina species), which itself acquires the parasites from human or animal hosts. The vector and the disease are confined to sub-saharan Africa where the disease occurs in endemic foci from which epidemics arise. Two forms of African trypanosomiasis in humans are recognized and both are fatal if left untreated. Control strategy is dependent on the capacity of the public health services to diagnose and treat cases, and the maintenance of surveillance is essential if epidemics are to be prevented. In epidemics this strategy should be extended to include vector-control measures to break transmission of the disease while cases continue to be diagnosed and treated. Eradication of the vector is not feasible nor can animal reservoirs be eliminated. National authorities must thus maintain surveillance to reduce the human reservoir of infection in order for low levels of endemicity, particularly in areas where epidemics have occurred in the past, to be retained.

Selective primary health care: strategies for control of disease in the developing world. IX. Poliomyelitis.

Poliomyelitis is an acute viral disease primarily afflicting children. It can be very mild, permanently crippling, or fatal. In the developed nations, poliomyelitis is controlled by the use of trivalent vaccines: killed virus administered by injection and/or attenuated virus administered orally. The latter is cheaper. A combination of the two may be required in some tropical countries. In many developing nations poliomyelitis remains endemic and prevalent, especially in children; 37,747 cases were reported to the World Health Organization in 1979, but greater than 200,000 cases probably occurred. Socioeconomic improvement and public health measures (i.e., immunizations) remain the major strategies for control. While global eradication may be a more distant goal, poliomyelitis could be controlled better. Effective programs for control include safe, efficacious, and inexpensive vaccines; methods for successful management of vaccine delivery systems; commitment and training of health personnel; public education; commitment of funds; and research to improve vaccines and their delivery. The major obstacle to control of poliomyelitis is failure to immunize an adequate number of susceptible children. Development of strategies for immunization is crucial to elimination of poliomyelitis as a major world health problem.

Selective primary health care: strategies for the control of disease in the developing world. VII. Filariasis.

At least 250 million people throughout the world are infected with filariae, and the number of such persons is increasing. Three species infect humans: Wuchereria bancrofti, Brugia malayi, and Brugia timori. The peak of microfilarial density in the blood usually occurs nocturnally. Transmission of filariasis is remarkably inefficient. In an endemic area, approximately 100,000 mosquito bites yearly are required for production of each new case of microfilaremia. Only a small proportion of those infected suffer any ill effects from these worms. Clinical filariasis can present with acute inflammation such as lymphangitis and lymphadenitis and with chronic lymphatic obstruction such as hydrocele and lymphedema of the limbs. Measures available for potential control include the widespread usage of mosquito nets, vector control, and chemotherapy with diethylcarbamazine. Unfortunately, the efficacy of the first of these is untested and the latter two are inadequate. More research is required on vector control, assessment of new drugs, and the development of vaccines.

Selective primary health care: strategies for control of disease in the developing world. V. Leprosy.

Leprosy afflicts 10-15 million people in the world, primarily in tropical and subtropical developing countries. In areas endemic for leprosy, the incidence may reach four to six cases per 1,000 population, and the prevalence of the disease frequently exceeds 10 per 1,000 population in parts of Africa and Asia. While these figures are not high in relation to those for other tropical diseases, many developing countries consider leprosy a major health problem because a significant proportion of cases result in deformity and subsequent social stigmatization. Leprosy comprises a wide spectrum of clinical and pathologic stages that have been classified histopathologically. In polar lepromatous disease there is specific immunologic unresponsiveness of cell-mediated immunity to Mycobacterium leprae antigens, while, in the tuberculoid form of the disease, strong cell-mediated immunity is present but tissue damage seems to be a consequence. This review discusses the detailed immunologic analyses of the histopathology and pathogenesis of the various stages of leprosy. It will be argued that lepromatous leprosy presents an extraordinary model for understanding the mechanisms of immunologic unresponsiveness in humans. The present effectiveness and limitations of chemotherapy in the face of emerging resistance to dapsone are briefly discussed. Recent advances in the development of vaccines are discussed in terms of their immunologic potential and epidemiologic necessity. The implications of an effective prophylactic or immunotherapeutic vaccine used in combination with chemotherapy are also presented.

Selective primary health care: strategies for control of disease in the developing world. IV. Measles.

Measles, a highly contagious viral disease, kills several hundred thousand infants and young children yearly. Essentially all children will become infected; at least 1% of those living in developing countries will die unless protected by immunization. In urban areas, peak incidence occurs in those younger than three years. The youngest and most undernourished children suffer the most severe complications and the highest risk of death. Diarrhea, malnutrition, pneumonia, and blindness associated with vitamin A deficiency are the worst complications. The infection is preventable by the timely administration of a potent vaccine. This endeavor requires a well-managed technical and administrative network that remains difficult to organize in many areas of the world. The vaccine is efficacious and has few adverse effects but must be provided to children during the short interval between loss of transplacentally acquired antibodies and the acquisition of natural infection. The improvements in heat stability of the vaccine increase the likelihood of providing potent vaccine, but a well-managed cold chain remains a prerequisite for any successful immunization program. Health education, improved management skills, publicity, and community support are all important factors for ultimately preventing the morbidity and mortality from this disease.

Selective primary health care: strategies for control of disease in the developing world. III. Hepatitis B virus and its related diseases.

Hepatitis B virus (HBV) infects people throughout the world; the highest rates of infection are in sub-saharan Africa and east Asia. Morbidity and mortality accrue from acute hepatitis, chronic hepatitis, and primary hepatocellular carcinoma. In the developing world most HBV transmission occurs during infancy or early childhood. The production of an effective vaccine against this virus opens a new arena for disease control. Vaccination, along with sterilization of medical instruments, could well lead to the interruption of HBV transmission.

Selective primary health care: strategies for control of disease in the developing world. II. Tuberculosis.

Tuberculosis remains a major public health problem throughout the world. Practically all adults in developing countries are infected with the organism Mycobacterium tuberculosis, but only about five percent suffer any ill effects. Morbidity and mortality are greatest during the economically and socially productive young adult years. Treatment requires multiple drugs and many months of compliance. Treatment both reduces transmission of the organism and allays suffering in the diseased individual. The efficacy of vaccination with BCG (bacille Calmette-Guérin) remains controversial, but several trials have demonstrated some reduction in clinical disease. At this point, the ideal disease control program entails several steps of epidemiologic assessment of the problem and resources, development of public health orientation in the professional community, treatment of infectious patients, and BCG vaccination of all those under 15-20 years of age.

Selective primary health care: strategies for control of disease in the developing world. I. Schistosomiasis.

The control of schistosomiasis should be related to its unique biology and ecology. Whereas schistosomes multiply within the snail intermediate host, they do not replicate within the mammalian definitive host. As a consequence, a large proportion of infected humans have low or moderate worm burdens, the disease tending to occur in the small proportion of individuals harboring large numbers of worms. This situation suggests an unusual strategy: the control of schistosomal disease rather than the usual approach of control of infection and its almost invariable end point of eradication. Control of infection (transmission) requires use of mollusciciding, provision of water supplies and sanitation, health education, and chemotherapy and is still highly unlikely to result in eradication. Control of disease can be achieved at far lower cost by chemotherapy alone using the newer single-dose, oral, nontoxic chemotherapeutic agents.

Selective primary health care: Is efficient sufficient?

Developing countries are increasingly using economic evaluation methods to assess and plan their health services. Inappropriate application of these methods may lead to serious errors in developing primary health care strategies. In ‘Selective Primary Health Care’, Julia Walsh and Kenneth Warren present a logical approach to health planning based on cost-effectiveness techniques. Their paper is a timely example of the risks of using simple technical criteria to plan solutions to complex public health problems. Cost-effectiveness is not a sufficient criterion for planning primary health care. Related issues are discussed in these comments. As an alternative, a multiple-objective approach is suggested.

Selective primary health care: Old wine in new bottles

This paper comments on a previous paper on selective primary health care (PHC) written by Drs. Walsh and Warren. The PHC approach as developed under the guidance of the World Health Organization (WHO) represents the key health services/sector component of the basic needs strategy. This author finds that the lack of analytical rigor in the critical paper is a serious flaw. Another criticism is levelled against them with regard to established priorities for health care. In discussing feasibility of control the meaning implied is the technical possibility of controlling a disease through vaccine spraying or chemotherapy. To a health planner this appears quite differently. A vaccine is insignificant if the health care network is not in contact with the masses. Resource availability (finances trained workers etc.) and allocation are the context in which all of this must be considered. Once the diseases to be treated and prevented have been selected the next step is to devise interventions of reasonable cost and practicability. This does not take into account true considerations for those factors. Comprehensive PHC as understood by Walsh and Warren is probably not going to be available for everyone in the near future. However by implying that basic PHC systems are beyond the reach of low income countries is an error. Selective PHC is the authors maintain potentially the most cost-effective type of medical intervention and the authors recommend a mix of health care activities. This proposal is different in that it provides services for a certain group within the population (young children up to age 3 and women of childbearing age) while preventing or denying others. This in itself would be quite difficult to accomplish. This author maintains that it is virtually impossible to conceive of circumstances which would justify a fixed unit carrying out only a very narrow range of activities as proposed by Walsh and Warren. Clearly the authors are correct when they observe that flexibility is necessary; that certain types of care and treatment should be added when they become available or subtracted when they are not longer needed. The existing health care infrastructure which already exists in most countries is being ignored as is the possibility of its great expansion in this decade. Nor does the original paper address the nature of the wider development process. The priority activities advocated by Drs. Walsh and Warren are quite compatible; with the balanced set of PHC development; these may be essential for the successful extension of these high priority activities to the mass of low income country populations.