Since diarrhoeal disease is often epidemic it was necessary to adopt a more flexible approach in the program to ensure that outbreaks and epidemics of diarrhoeal disease could be quickly investigated. The primary studies have determined the aetiology of diarrhoea in patients admitted to Goroka Base Hospital and it was planned subsequently to investigate these organisms in carriage studies in epidemiologically defined rural communities of the Asaro Valley from which the Goroka Hospital draws its patients. However, delays in analysis have led to delays in the initiation of this phase of the project. The role of pigs as a reservoir and amplification site for enteric infection has been examined. Enteric bacteria, viruses and parasites have all been investigated in the laboratory. The program has achieved new findings on rotavirus, Campylobacter and Cryptosporidium. Pathogenic strains of Escherichia coli and enteric adenoviruses have been studied. The water in which sweet potato has been cooked was found to be acceptable as an oral rehydration fluid in preliminary studies, but further evaluation has not yet been undertaken. Attitudes to diarrhoea and to the acceptance of particular interventions have been examined. Behaviour patterns that may be relevant to the transmission of different organisms have been studied in detail using a case-control methodology. Because of recent financial constraints further work on diarrhoeal disease has been deferred.

The bacteriology unit has studied peptic ulceration, which is very common in parts of the highlands, and the association between both gastritis and gastric ulcer and Helicobacter pylori infection has been confirmed in PNG patients.

Intestinal parasitic infections are widely prevalent and lead to considerable morbidity. The distribution of hookworm, Ascaris and other parasitic infections, their treatment (leading to a change in standard management) and their interaction with nutritional factors were studied. Separately funded, collaborative studies on hookworm infection, and the relevant human immune responses, are currently being carried out in a coastal population.

Blastocytis hominis was found to be a very common parasite in the highlands though its role in producing disease has not been proven. A parasite of particular interest is Strongyloides fuelleborni kellyi, which causes the swollen belly syndrome, a disease apparently peculiar to Papua New Guinea.

The parasite has been shown to be widely distributed, though not found in all areas. Work has been completed on the biology and taxonomy of this organism. Its mode of transmission has still to be worked out. The tapeworm Taenia solium, from which originates the disease cysticercosis, is not found in Papua New Guinea, but has been introduced to Irian Jaya. There is consequently concern over the possibility of its crossing the border, and the infection has been sought in refugee communities. More systematic and regular surveillance is urgently required.

Pigbel, or enteritis necroticans, is a necrotizing disease of the small bowel caused by the beta-toxin of Clostridium perfringens type C and promoted by a generally low-protein diet and by heat-stable trypsin inhibitors present in sweet potato, the main staple of the highlands. It was the commonest cause of death in highlands children over the age of one year. The Institute helped develop a vaccine against pigbel and then evaluated it in the field. The vaccine was shown to be successful in preventing pigbel and is now part of the routine immunization program in the highlands provinces. Since the introduction of the vaccine there has been a dramatic drop in the incidence of pigbel, and this has continued to the extent that doctors now working in the highlands hospitals have become less familiar with the disease. Unfortunately, the country ran out of pigbel vaccine after the original supplier ceased production. Though a new source has been found there have been long delays in obtaining supplies of the vaccine. The Institute has agreed to carry out studies to check its safety and immunogenicity and these should begin in 1999.

Typhoid became an increasing problem some years ago, particularly in the highlands. The Institute evaluated a slide agglutination test for the diagnosis of typhoid that could be used in health centres, but its diagnostic discrimination was lost with the marked increase in the endemicity of typhoid. Reevaluation has established a new appropriate cut-off titre, but the test now requires hospital-level laboratory facilities to carry it out. An epidemiological study of typhoid, with a defined demographic base in the Asaro Valley, has determined the very high incidence of typhoid, identified carriers, who were mainly convalescent patients, and established the sources of infection in the community. It is planned to use this epidemiologically characterized population for the future evaluation of new typhoid vaccines. Though budgetary constraints have forced a reduction in the scope of the enteric diseases research program, every effort has been made to maintain activities on typhoid. Studies are being undertaken on new diagnostic tests for typhoid, on molecular typing of Salmonella typhi and on the relationship between strains of Salmonella typhi and clinical severity. A study is planned on the use of fluoroquinolone antibiotics in typhoid: by improving compliance with treatment and by reducing the convalescent excretion of S. typhi, these drugs, though expensive, may prove to be more cost-effective than chloramphenicol in the management of typhoid.