War Surgery and Medicine
CHAPTER 9 — Hookworm (Ankylostomiasis)
HUMAN ankylostomiasis is caused mainly by two species of blood-sucking nematodes—Ankylostoma duodenale and Necator americanus. Both are found on the mainland of Northern Australia, in New Guinea, and in most of the Pacific Islands. The nematodes attach themselves to the mucous membrane of the duodenum and jejunum and cause small haemorrhages. The eggs are passed in the faeces and develop as they are passed and in the soil, especially in hot, moist conditions, into filariform larvae. These infect man commonly by burrowing through the hair follicles of the skin of exposed parts, and sometimes by ingestion. When skin invasion occurs, the larvae travel by the blood to the lungs, then burst into the alveoli and so reach the oesophagus and alimentary canal. Eggs appear in the stools seven to ten weeks after skin infection.
The symptoms consist of (a) ground itch, generally seen in the feet, and less commonly in the arms, producing intense itchiness, redness, brawny swelling and a papular and vesicular eruption lasting two weeks; (b) upper abdominal symptoms; (c) anaemia. In mild cases no symptoms may arise before six months and then consist only of mild dyspepsia and fatigue. In severe cases symptoms may develop in ten to twenty weeks with marked fatigue and fainting attacks, and possibly some enlargement of the liver. The skin and nails may be dry, and oedema of the feet and ankles and puffiness of the face are common. Circulatory changes with rapid weak pulse and dilatation of the heart occur. The digestion is upset and constipation is the rule, with at times intermittent diarrhoea. The blood changes consist of an anaemia of hypochromic microcytic type, at times severe. Eosinophilia is the rule, ranging from 10 to 40 per cent, less marked in chronic cases.
Diagnosis is made either by routine stool examination, or by the detection of eosinophilia, or else by a history of ground itch, anaemia and dyspepsia.
Treatment consists in giving antihelminthic drugs. Three are commonly used: tetrachlorethylene, carbon tetrachloride, oil of chenapodium. The latter is commonly used in conjunction with either of the others. The drugs are given on an empty stomach, page 563 generally first thing in the morning, followed by a saline purge. Tetrachlorethylene is the least toxic, and no ill effects have been noticed in the free use of the drug, even in the forward areas. Anaemia is treated by giving a well-balanced and liberal high-protein diet and also iron in large doses.
Prophylaxis consists of the prevention of skin infection by wearing boots at all times, especially on river banks and the seashore, by camping only on clean ground, and by the protection of water and food supplies from contamination.
2 NZEF (IP) Experience
The occupation of Nissan Island led to the development of hookworm in a considerable percentage of the New Zealand troops involved. Early in April 1944 a large proportion of the men of 30 Battalion were beginning to complain of vague gastro-intestinal symptoms, consisting chiefly of malaise, upper abdominal pain, anorexia, nausea and vomiting, general apathy, and loss of energy. This led to an investigation, including the taking of blood counts, the latter disclosing the presence of eosinophilia varying from 6 to 62 per cent, anything above 5 per cent being treated as abnormal. The battalion had spent five months in static occupation of Vella Lavella, and had landed on Nissan in the middle of February, living in a primitive condition in the jungle for the first fortnight's fighting. The natives of the island were known to be heavily infected with hookworm.
Of the 661 men examined, 32 per cent were shown to have eosinophilia above 5 per cent. A group of those with high eosinophil counts was evacuated to 2 NZ CCS for further investigation, which showed that ankylostomiasis was the most likely cause of the symptoms and the eosinophilia, but only 10 per cent of the cases revealed ova in the stools, probably due to the short interval following infection. A survey was then carried out of all cases of New Zealand troops on Nissan and blood films examined by the Field Ambulances. The evacuation of all cases of eosinophilia to Guadalcanal was thought to be unwarranted, and treatment was carried out on Nissan by the RMOs, 4 c.c. of tetrachlorethylene being administered, followed by magnesium sulphate aperient, with no untoward results. A number of men with high eosinophil counts were evacuated to New Zealand in returning drafts without treatment.
Approximately 2700 troops were evacuated before their differential count could be carried out. Of the 4169 men examined, 884 showed eosinophilia greater than 5 per cent, which was 21 per cent of the total examined. On this basis there would have been page 564 567 untreated eosinophilias in the 2700 troops sent back to New Zealand. The degree of eosinophilia in the 884 cases was:
|6-10||11-20||21-30||31-40||40 and over|
|Percentage of positive cases||47||34||12||5||2|
Three battalions (30, 35 and 37), the units most exposed, produced 574 cases, nearly two-thirds of the total of 884.
A report on the survey stated that during the first eight days of fighting all troops were sleeping on the ground, and 90 per cent complained of a papular, sometimes a pustular, rash about the ankles. The percentage in the companies affected by eosinophilia varied from 15 to 50 per cent, the higher percentage being in those engaged in combat. Clinically the severity of the symptoms varied considerably, the most characteristic being epigastric pains, loss of appetite, and ankle rash. Colonel Sayers, the Consultant in Tropical Diseases, considered that the rash that was noted on Nissan was probably not associated with the ankylostoma, and that the eosinophilia may not all have been due to the infection. He pointed out that hookworm did not necessarily cause eosinophilia, while other intestinal worms did. However, he considered that the symptoms of the Nissan cases strongly suggested hookworm infection. An American division after twelve months in the South-West Pacific had an average of 46 per cent of eosinophilia, and of those cases 56 per cent had hookworm ova in the stool on one examination, and 76 per cent after two examinations.
A survey was carried out at 4 General Hospital, New Caledonia, by Lieutenant-Colonel M. Williams and Captain M. W. A. Gatman of the patients who had been on Nissan Island. Two groups were investigated. One was a group of 54 found on Nissan to have more than 5 per cent eosinophil cells and treated at 2 NZ CCS, where hookworm ova were found in the stools in only three instances. In blood counts at 4 General Hospital on 46 of the cases, eosinophils showed a significant decrease in 9 cases, a significant increase in 8 cases, and no change in 25 cases, with 8 indeterminate. The range of eosinophils had changed from 6 to 62 per cent to 2 to 40 per cent, and the average from 15.5 per cent to 14.3 per cent. Up to three stool examinations in the 54 cases showed 14 men with abnormal intestinal parasitology—strongyloidiasis, 6; ankylostomiasis, 3; trichuriasis, 2; amoebiasis, 3. The other group comprised 80 cases who had all been on Nissan, of whom half had had blood examinations without eosinophilia being found and half had had no previous investigation. In 12 of these cases the eosinophil count exceeded 5 per cent, the range being 6 to 23 per cent and the average 10.9 per cent. Stool examinations page 565 in this group revealed trichuriasis in 5 cases and amoebiasis in 3. The general picture of this survey was confused by the variability of the subjects, but it was thought that probably a high proportion of cases of eosinophilia were not due to hookworm infestation.
Future of the Infection in New Zealand
Colonel Sayers considered there was little danger of hookworm infestation being spread in New Zealand by returning troops. The ova were not infective, and the infective filariform larvae did not develop for five days following excretion, so that re-infection of the individual or infection of other people by contamination of food handled by an infected person could not occur. The only method of infection was through the skin, or by eating food contaminated by the larvae. Hookworm normally die out gradually in the bowel, the maximum egg production occurring in six months, and the egg count dropped by 92 per cent in five years. Only when a sewerage system or septic tank was not used would any danger of spread arise. The only possibility of trouble might be in mines.
The experience of the Pacific Force showed the necessity to be on the alert for the development of hookworm infestation, although in its experience no serious trouble arose.