The Preventive Medicine Division, Office of the Surgeon, USARV, was organized late in 1965 to advise the command on the incidence, prevalence, and epidemiological aspects of diseases which were likely to occur among U.S. Army combat soldiers and, therefore, to be hazardous to military operations in Vietnam.

The 20th Preventive Medicine Unit (Field), formerly the 20th Preventive Medicine Laboratory, was the first preventive medicine unit deployed to Vietnam. Originally this unit and later four preventive medicine detachments functioned independently, but late in 1967, higher echelon technical support was required and the four detachments were assigned to the 20th Preventive Medicine Unit which then assumed responsibility for the countrywide US Army preventive medicine program. When the 172d Preventive Medicine Unit (Field) became operational on 29 July 1968, the responsibility for preventive medicine support in Vietnam was divided between the two units. Both units were assigned to the 44th Medical Brigade, and each was augmented by two detachments, one control team and one survey team. Thus, countrywide deployment followed, from Quang Tri in the north to Can Tho in the south.

Malaria

Steady progress in the reduction of malaria in Vietnam had been possible through vigorous command emphasis, improved preventive regimens, and increased control measures. A major change in the chloroquine-primaquine chemoprophylaxis program was instituted with Change 1 to USARV Regulation 40-4. This change stipulated that units in high-risk areas were to take daily dapsone tablets in addition to weekly chloroquine-primaquine tablets as chemoprophylaxis against Plasmodium falciparum, the malarial parasite responsible for nearly 98 percent of infections occurring among troops. The command surgeon notified field commanders to enforce this change when manpower losses due to infections with P. falciparum were greater than 20 cases per 1,000 per annum per major unit.

The Wilson-Edeson test, adopted by the 172d Preventive Medicine Unit, to measure the amount of chloroquinc in urine, was rapid and

convenient for field use. This test helped field commanders evaluate objectively each unit's malaria chernoprophylaxis program and resulted in a dramatic drop in the malaria rate in the units tested. Since slightly more than 80 percent of all cases of malaria occurred in combat units, it was the responsibility of field commanders to provide consistent and continuous command emphasis on preventive measures. In addition to chloroquine-primaquine and dapsone chemoprophylaxis, personal protective measures to control malaria were stressed. Skin repellents, aerosol insecticide dispensers, bednets, and headnets were in general use by field units. Combat units in remote forward areas received repellents and aerosol dispensers routinely.

For personnel departing Vietnam, commanders were urged to insure that the malaria chemoprophylaxis records of all returnees were reviewed as soon as possible after arrival at their new duty station to make certain that each returnee had signed a "malaria debriefing" statement. This procedure was recommended to prevent manpower loss and to limit the spread of malaria from infected soldiers to susceptible persons in the United States and other areas. Those individuals who had not completed the 8-week chloroquine-primaquine course and the 28-day dapsone course were to be given sufficient tablets to complete the malaria chemoprophylaxis course they were on in Vietnam.

Infectious Hepatitis

Beginning in 1966, all troops in Vietnam were inoculated with gamma globulin during their first and fifth months of assignment to control infectious hepatitis. Later, as the troop strength increased, a system of selective priorities was set up for the use of this serum, based upon the premise of the greatest need. Most cases of infections hepatitis were caused by rating or drinking contaminated food or water. The disease was of special concern when those infected were cooks or food handlers. Continuous efforts were made to inform all troops of the dangers inherent in consuming food purchased on the economy, where contact with the virus was unavoidable.

Diarrheal Diseases

The most common disease among US soldiers in Vietnam was diarrhea. The rate for this disease showed seasonal variations with peaks each year during May and June, but the greater numbers of cases were sporadic and were, usually caused by a breakdown in unit mess saturation or by rating procured vegetables contaminated with Shigella and Salmonella. No specific etiological agent was identified for most of the diarrheal cases admitted for treatment, Shigellosis accounted for most cases for which an agent could be identified.

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Measures were continued to improve mess and water sanitation and waste disposal practices, and to educate the soldiers in basic field and food sanitation. The use of disposable paper plates and plastic eating utensils eradicated a potential source of diarrheal disease- inadequately cleaned mess gear.

Skin Disease

Skin disease caused by prolonged exposure to wetness followed by secondary invasion of the injured tissue by fungal or bacterial agents was a problem among US Army ground troops fighting in inundated areas during the monsoon season. The Office of the Surgeon, USARV, recommended that all combat units be provided with zipper boots, inserts, and nylon socks. The most useful preventive measures were limiting participation in combat operations in wet areas to 48 hours, intensive foot care during the "drying out" period which followed, frequent changes of boots and socks, and prophylactic use of griseofulvin.

Fever of Undetermined Origin

Fever of undetermined origin was a major cause of morbidity in Vietnam. Elaborate studies were, initiated before 1966 in an attempt to identify the etiological agent: or agents involved. By 1968, through laboratory efforts, 40 percent of the admissions were identified as caused by arboviruses or other arthropodborne agents. The preventive measures used were insect sprays and bednets.

Rabies

As the US Army troop buildup in Vietnam increased, there was a concomitant rise in the number of animal bite cases treated in USARV medical facilities. The major difficulties were the sheer number of pets acquired by Americans, the large number of small units and detachments scattered among the, Vietnamese communities, and the lack of a meaningful civilian rabies control program. There were no cases of rabies among USARV personnel during 1965-70, although several thousand soldiers received the antirabies vaccine prophylaxis when the biting animal was not apprehended.

To control rabies in pets, the preventive medicine rabies control program required that each unit commander determine the number of animals to be allowed in his area, that all animals be registered, and that each animal be vaccinated against rabies and restrained within the unit area. Little restraint of pets was ever noted in Vietnam.

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Other Communicable Diseases

Other communicable diseases; of, special concern occurred in Vietnam and could have become a threat with the increase of troop strength and acceleration of combat operations without an effective preventive medicine program.

The admission rates for common respiratory disease and influenza remained relatively moderate from 1965 to 1970. Although an outbreak of influenza in Hong Kong in July 1968 was caused by a strain of influenza virus sufficiently different to warrant concern ever a probable pandemic, only a few cases appeared in military units in Vietnam. The monovalent vaccine became available in limited amounts in January and February 1969.

Melioidosis, a glanders-like disease observed in rodents and occasionally in man, was rarely encountered by the Army before deployment of troops to Vietnam. Pseudomonas pseudomallei, the causative agent of melioidosis, was cultured from samples of oil, market fruits and vegetables, well water, and surface water. These may have been the source of infection since man-to-man transmission was not observed. Recognition and early treatment were the prime factors in reducing the melioidosis mortality rate in 1968.

Dengue fever was reported in small numbers during 1966, and scrub typhus cases, in even fewer numbers. Immunization against typhus, routine since late 1962, was temporarily discontinued on 25 February 1969, because available vaccines were not potent enough to protect individuals against louseborne typhus fever.

Although both cholera and Plague were prevalent during 1966 among the, civil population of Vietnam, no cases of cholera occurred among US troops from 1965 to 1970. As of 19 April 1968, five confirmed cases of plague and one unconfirmed case had occurred among US Army personnel.

Field Sanitation Training

Instructors in preventive medicine units and detachments continuously stressed basic hygiene and sanitation, malaria chemoprophylaxis, insect and post control, waste disposal, and unit and individual protective measures against arthropodborne and waterborne diseases as well as other health hazards that caused discomfort to troops or damage to materiel.

Water Supply Surveillance

Major emphasis was placed on medical surveillance of field water points and cantonment water supply systems. Preventive medicine units provided first-echelon surveillance of water supplies for organizations

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without assigned medical personnel, and second-echelon surveillance of water supplies for all others. The USARV requirement for free available chlorine in, water was strictly enforced: 5.0 parts per million after 30 minutes contact at field water points and 2.0 parts per million at field consumption points.

Preventive medicine units also provided medical surveillance of iceplants, including residual chlorine and bacteriological testing of the quality of water. Ice consumed or used for chilling foods and beverages was supplied by iceplants operated by the Army or by Army-approved local civilian firms.

Waste Disposal Practice

Monitoring waste disposal practices was another important preventive medicine activity; no major breakdowns in the waste disposal systems were related to disease outbreaks. In general, field units used urine soakage pits, with or without "urineoils," and "burn-out" latrines for the disposal of human excreta. For liquid wastes, oxidation ponds and sewage, lagoons were used as well as septic tanks with soil absorption beds. Refuse- garbage, trash, kitchen wastes- was disposed of in. sanitary fills. Infections wastes from hospitals and other medical facilities were disposed of in high-temperature incinerators or by special packaging and burial.

Food Service Sanitation

Messkit sanitation procedures were, almost totally unnecessary in Vietnam. Troops provided with rations used plastic trays, paper plates, or, in rare cases, chinaware. The individual combat meal (C-ration) was usually eaten with the utensils provided with the ration. The use of food service disinfectants, an item of special interest for USARV annual general inspections, was emphasized.

Pest Control Measures

Pest control in USARV was an integrated program involving the coordinated efforts of unit field sanitation teams, contract engineer entomology services, and preventive medicine units and detachments. Unit self-help sparked by trained field sanitation teams was the backbone of the program. In addition to pest control, preventive medicine person-

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nel provided first- and second-echelon support to unit programs and insured that field sanitation teams were trained. Contract engineer entomology services were provided at major installations and base camps throughout Vietnam by Pacific Architects and Engineers and by the Philco, Ford Company. Preventive medicine units conducted ground fogging and mist operations in remote areas where contract entomology services were lacking. Close liaison and cooperation were encouraged by medical entomologists with engineer entomologists to insure rapid exchange of information. The engineer program was unique in that it was the first time in recent history that the mission of pest control had been given on a broad scale to a civilian contractor in a combat zone.

Quarantine and Inspection Procedures

Early in the 1960's, the Armed Forces Pest Control Board was designated the coordinating agency for development of appropriate insect and rodent control programs for the Armed Forces. The Armed Forces had become increasingly aware of the real threat of accidental importation into the United States from Vietnam of pests and diseases of agricultural and medical concern. The inherent problems of inspecting vast quantities of cargo at US ports of entry demanded the establishment of a preshipment quarantine inspection program for military cargo. Quarantine inspection of vessels, aircraft, and retrograde cargo in Vietnam was part of a cooperative preventive medicine program between the Department of Defense, the USPHS (US Public Health Service), and the USDA (US Department of Agriculture) during 1969. More than 350 medical personnel of the Army, Navy, and Air Force were trained and certified as USPHS and USDA quarantine inspectors. A 24-hour daily inspection service was maintained at major maritime and aerial ports operated by the Armed Forces for incoming and outgoing cargo. In addition, by special arrangement, cargo shipments were inspected and certified at auxiliary ports located throughout Vietnam.

Three USARV preventive medicine conferences were held during a 12-month period in 1968 and 1969. These 1-day conferences were conducted as working seminars and included formal presentations and informal study groups. About 75 individuals attended each conference. Besides participants from all USARV commands, there, were preventive medicine representatives of the Surgeon, USMACV; AID; and ARVN. The seminars and panel discussions covered all phases of preventive medicine and provided the means for exchange of information and the opportunity to profit from the experience of personnel in different areas of Vietnam.