Operational Medicine Medical Education and Training

Environmental Diseases and Injuries II





Throughout history, infectious organisms have plagued society. Biblical accounts of plagues attest to this fact. In London in the 1600s, the Black Plague killed thousands of people.

In a combat situation, the impact of disease on the combat soldier cannot be overstated. In every war in which the American soldier has fought, there have been more casualties caused by disease than by combat wounds. An outbreak of a simple intestinal disease in a combat zone can greatly affect the morale and fighting strength of the Army.

Information concerning the identification, treatment, and preventive measures for arthropod-borne, animal-borne, and helminthic diseases will be discussed in this subcourse. As a Medical NCO, it is extremely important that you are aware of the prevention and treatments for the numerous diseases which you will encounter. With the awareness of those diseases, their general characteristics, modes of transmission, and clinical findings, you may be alert for either treatment or prevention.


Length: 79 Pages

Estimated Hours to Complete: 7

Format: PDF file

Size: 0.4 MB


Anyone may take this course. However, to receive credit hours, you must be officially enrolled and complete an examination furnished by the Nonresident Instruction Branch at Fort Sam Houston, Texas. Enrollment is normally limited to Department of Defense personnel. Others may apply for enrollment, but acceptance is not guaranteed.


Environmental Diseases and Injuries II

Distance Learning Course
79 Pages
Est. 7 Hours
0.4 MB pdf file

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Adult Anopheles Mosquito





Section I. Fly-Borne Diseases

Section II. Tick-Borne Diseases

Section III. Louse-Borne Diseases

Section IV. Flea-Borne Diseases

Section V. Mosquito-Borne Diseases





Section I. Roundworm (Nematode) Diseases

Section II. Tapeworm (Cestode) Diseases

Section III. Fluke (Trematode) Diseases









Arthropods are any of the insects, arachnids, or crustaceans consisting of a jointed body and limbs with the brain dorsal to the alimentary canal and connected with a ventral chain of ganglia. The source of the arthropod-borne disease is known as the reservoir. The vector, usually an arthropod, transmits the causative organisms of disease to a susceptible person. The organism on which the parasite lives and from which the parasite obtains its nourishment is called the host. Autoinfection describes an infection by bacteria that is present within one's own body.


a. Transmission. Diseases are transmitted by houseflies on their hairs and in their feces and vomitus. Flies breed in manure, human waste, and decaying organic matter. This decaying organic matter is defined as the fly's host since it provides the fly with nourishment. Flies ingest the solid food by vomiting the contents of their stomach onto the food and then sponging it up.

b. Diseases. Dysentery, cholera, and typhoid fever are the most important diseases transmitted by flies.


a. Dysentery.

(1) General. Dysentery is the term applied to a number of intestinal disorders (especially of the colon) that are characterized by inflammation of the mucous membranes. It is a common disease that is often self-limiting and mild but can be serious for babies up to 3 years old. A rise in strains of dysentery which are resistant to multiple antibiotics has been noted recently.

(2) Signs and symptoms. Dysentery usually begins abruptly and the patient has diarrhea, and suffers lower abdominal cramps and tenesmus. Blood and mucus are often found in the diarrheal stool. Other symptoms include fever (up to 104F in young children), chills, headache, and lethargy. Meningismus, coma, and convulsions occur in the most severe cases. Dehydration, weakness, and a tender abdomen follow as the illness progresses. In infants, dehydration, acidosis, and electrolyte imbalance occur.

(3) Treatment. The antibiotic of choice is ampicillin (100 mg/kg/d) which can be given for 5 to 7 days orally in 4 divided doses. If there is improvement, do not continue with the medication any longer even if the stool cultures are still positive. Other medication effectively used in treating dysentery are tetracycline, chloramphenicol, or co-trimoxazole. Actually the use of even mildly toxic antibiotics is usually not justified because the majority of cases are mild and self-limited. For all moderately or severely ill patients, parenteral hydration and correction of acidosis and electrolyte disturbances are a necessity. Give clear fluids for 2 or 3 days after the bowel has been at rest for a short time and offer the patient small frequent feedings with a diet that is soft and easily digestible. Whole milk, high residue, and fatty foods should be avoided. If cramps are severe, anti-spasmodics (i.e., tincture of belladonna) may be helpful. Place the patient on effective stool isolation precautions to limit the spread of infection.

b. Cholera.

(1) General. Cholera is an acute bacterial diarrheal disease of the small intestine. Cholera is caused by Vibrio cholerae which are transmitted by food or drink that is contaminated by feces containing a large number of vibrios. These vibrios produce a powerful exotoxin in the small intestine (in particular, the ileum) where they grow. The reduction of the sodium reabsorption causes massive diarrhea that is fatal in 50 percent of cases if untreated. This exotoxin induces hypersecretion of water and chloride in the small bowel.

(2) Signs and symptoms. Cholera victims experience a sudden onset of painless, watery diarrhea of up to 15 liters per 24 hours. The liquid stool is grayish containing mucus and food particles. There is no fecal odor, blood, or pus, but rapid dehydration takes place. The patient may have occurrences of vomiting and becomes markedly dehydrated and acidotic. His eyes are sunken and he experiences intense thirst, hypotension, a subnormal temperature, oliguria, shock, muscle cramps, and coma.

(3) Treatment. The loss of water and electrolyte must be restored immediately and continuously, and acidosis must be corrected. Replacement of oral fluids (same volume as that lost) may be possible in the moderately ill patients. If the patient is unable to take fluids by mouth, an I.V. infusion of Ringer's lactate must be used to replace the fluids until the blood pressure and circulating blood volume are restored. The medication used to suppress vibrio growth and shorten the time of vibrio excretion is tetracycline, 0.5g given orally every 6 hours for 3-5 days. If untreated, cholera lasts 3-5 days and has a mortality rate of up to 80 percent. If the victim receives prompt and competent treatment, however, the mortality rate can be reduced to 1 percent. The health department must be notified if it is suspected that a victim has cholera.

(4) Prevention. The cholera vaccine consists of 2 injections of 0.5 and 1 ml. intramuscularly or subcutaneously 1-4 weeks apart, then a booster dose of 0.5 ml is administered every 6 months when cholera is a hazard. Even so, the vaccine offers only limited protection and has no value in controlling outbreaks. All water, other drinks, food, and utensils must be boiled or avoided in endemic areas. When high standards of sanitation and public health exist, there is rarely an outbreak of cholera of any significant size.

c. Typhoid Fever.

(1) General. The gram-negative rod Salmonella typhi causes typhoid fever when it enters the victim's gastrointestinal tract, penetrates the intestinal wall, and produces lesions and inflammation of the mesenteric lymph nodes, spleen, and small intestines. The organisms can localize in the kidneys, central nervous system, the gallbladder, or the lungs with inflammation. The Salmonella typhi is transmitted by consumption of food or drink contaminated by food handlers who are healthy carriers. The chronic carriers with persistent gall-bladder or urinary tract infections are the main source of most infections.

(2) Signs and symptoms. The onset of typhoid fever is insidious but can be very abrupt (especially in children) with a sharp rise in temperature with chills. If untreated, typhoid fever can be divided into three stages: the prodromal stage, fastigium, and the stage of defervescence.

(a) Prodromal stage. The victim experiences increasing malaise, headache, sore throat, diarrhea or constipation, abdominal pain, vomiting, and the fever ascends in stepladder fashion with each day's maximum higher than the preceding day.

(b) Fastigium. The fever stabilizes after 7-10 days, and the victim becomes quite sick. He is motionless and unresponsive, has half-shut eyes, and appears wasted and exhausted. He has marked abdominal distention along with "pea soup" diarrhea or severe constipation.

(c) Stage of defervescence. The victim surviving the fastigium stage (with its severe toxemia) without complications may show improvements gradually. His feverish temperature descends to normal in 7-10 days, and he becomes alert. Relapse may occur as much as 1-2 weeks after the temperature returns to normal, but the relapse is usually milder than the original illness. There is a possibility of having a cardiac arrhythmia. In about 10 percent of the patients, rose spots (rounded, rosecolored spots that blanch on pressure) appear between the 7th and 10th day of illness. These spots last from 2 to 5 days and then disappear.

(3) Complications. There are complications in approximately 30 percent of the untreated cases, and these account for 75 percent of the deaths from typhoid fever. During the third week, intestinal hemorrhage can occur with a resulting sudden drop in temperature, sometimes a sudden rise in pulse rate, pallor, sweating, hypotension, and abdominal pain. Other symptoms of less frequency include urinary retention, myocarditis, pneumonia, nephritis, thrombophlebitis, psychosis, cholecystitis, spondylitis (typhoid spine), and meningitis. Intestinal perforation, the most frequently fatal complication, is most common during the third week in adult males. Sharp abdominal pain occurs suddenly (usually in the right lower quadrant) with nausea, vomiting, fall in temperature, rapid pulse, and muscle spasm.

(4) Prevention. Typhoid immunization should be provided for household contacts of a typhoid carrier, for individuals traveling to endemic area, and during epidemic outbreaks. The vaccine consists of 2 injections of 0.5 ml each, subcutaneously, 4 weeks apart. Carriers of typhoid are not permitted to handle food.

(5) Treatment. Administer ampicillin in 4 equal doses per day, 1 dose every 6 hours for 14 days. Each dose is 25mg/kg. Another medication for typhoid fever is chloramphenicol, 1 g, which is given every 6 hours orally or it may be given intravenously until the fever disappears. After this, give chloramphenicol for 2 weeks at 0.5 g every 6 hours (for children, 50 mg/kg daily). If the infection is resistant to ampicillin and chloramphenicol, the victim may respond to trimethoprim-sulfonamide mixtures. The patient should have a high-calorie, low-residue diet, and his skin must have care. It may be necessary to administer parenteral fluids in order to supplement oral intake and maintain urine output. If the patient is severely toxic, administer hydrocortisone, 100 mg intravenously every 8 hours.

From Environmental Diseases and Injuries II


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