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CHAPTER 6
Filariasis

FILARIASIS is due to a nematode worm Filaria Bancrofti, which exists in man in two forms—microfilaria in the blood and macrofilaria in the lymphatic system. The intermediate host is a mosquito, Culex fatigans and Aedes aegypticus in the Pacific, in which the worms develop and then enter the human body through the mosquito bite. The worms mechanically block the lymphatics and secondary infection arises. Reproduction is slow, taking generally two to three years, and it is therefore years before the microfilaria can be demonstrated in the blood.

Clinically the infection is shown by attacks of fever, with severe headache, aching in the limbs, and occasionally rigors, lasting a week and recurring once or twice a year—the Mu Mu of the Samoan. The next stage is lymphangitis of the arm or leg, with swelling and redness and enlarged glands, fever, headache and rigors. Testicular symptoms may also appear, with pain; followed much later by swelling and hydrocele. Finally, at a very late stage, elephantiasis with very marked swelling of the limbs or scrotum may arise. A mild eosinophilia may be present.

Filariasis has for a long time been recognised as an important endemic disease in the Pacific islands, especially in Samoa, Tonga, and Fiji, where the development of elephantiasis makes the condition so obvious. New Zealand troops were used to garrison both Fiji and Tonga during the war for considerable periods, but there was little incidence of the disease.

There were no cases of filariasis in 3 NZ Division. In New Caledonia thick blood film examinations for filaria were carried out on 700 men who had served for at least one year in Fiji, and who by that time had been away from that area for at least twelve months. All films were negative. In the RNZAF one case of filariasis was invalided from the Solomon Islands, and also three cases of suspected filariasis, the diagnosis of which could not be confirmed.

A few cases of filariasis were boarded and returned to New Zealand from Fiji and Tonga, but no case showed signs of elephantiasis or permanent swelling.

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Up to 1949 some 43 cases had been dealt with by the War Pensions Department, either because they had been down-graded at discharge or later applied for pension. Dr D. Macdonald Wilson found in a survey that there were 37 Army and six Air Force personnel in the total. The Army cases served in the following Pacific islands: Tonga, 21; Fiji, 11; Gilbert and Ellice Islands, 4; Solomon Islands, 1. They arose first in the following years: 1942, 3; 1943, 24; 1944, 5; and 1945, 4. The periods spent in the tropics before the onset of the first symptoms were; under six months, 1 case; six months to one year, 20 cases; one to two years, 9 cases; two to three years, 8 cases.

As these cases arose mainly where laboratory facilities were not available, diagnosis was usually made on clinical grounds. Where laboratory facilities were available, either overseas or in New Zealand, there is no record of any specific diagnosis by positive blood findings. The patients suffered from swellings of the testes, epididymus, spermatic cord, and inguinal glands. Lymphangitis in the arm with swelling and pitting was common, along with enlarged epitrochlear or axillary glands. Only one case suffered from swollen legs and one case from swellings of the face. Sometimes the first symptoms were testicular pain preceding swelling of the scrotum, and when this condition subsided perhaps the next recurrence would be in the arm. No case was severe, and symptoms and swellings usually subsided in a week to a fortnight, allowing the patient to return to duty. However, the policy was to evacuate such cases out of the tropics back to New Zealand.

It was found that 19 of the 37 cases had no further attack after leaving the tropics, while 13 had recurrences of symptoms in New Zealand, but such recurrences had all ceased after two years—mostly within one year. In five cases the first evidence of disease was revealed after the return of a man to New Zealand, the period after return from the tropics varying from two weeks to six months.

There have been no cases with any serious residual symptoms. All except three cases suffered no symptoms of chronic filariasis in 1949, and none of these three had suffered an acute flare for some years, and their state appeared stationary. One patient was receiving a small pension (20 per cent) for a small residual hydrocele and slight swelling of testicle, and two others a 10 per cent pension for subjective pains in testes with slight thickening of the spermatic cord. Thus incidence was low and disability slight. Since the war new drugs with a specific action against the filaria have been introduced.