Tropical and Semi-tropical Diseases

Malaria
It is difficult to say what were the actual causes of the high incidence of the continued, remittent and intermittent fevers into which febrile diseases were classed in former days, but undoubtedly malaria must have been a potent cause. Though not actually describing malaria, Lind's advice on the prevention of tropical fevers is very pertinent. He observed that places situated near a morass or a river with low muddy banks were dangerous, especially when the air was full of insects and 'animaculae'. These were sure signs of the malignant disposition of the place. This was going a good deal further than the 'mala aria' (bad air) thought to be the principal cause of tropical fevers at that time, and which has given a name to the particular disease of malaria. To prevent sickness, Lind made the following fundamental observations:

'When ships are necessarily obliged to put into such unhealthy ports the first precaution is to anchor at as great a distance from the shore as can well be done, and to prefer the open sea, where the anchorage is safe, to running up rivers or bays enclosed with the land... the higher ships are sent up these rivers upon the coast of Guinea, the more sickly they become; such, however, as keep two or three leagues at sea, beyond the reach of the land breeze, are for the most part healthy.'

In his 'Essay on Diseases Incidental to Europeans in Hot Climates' Lind recommended that small doses of cinchona bark should be taken to prevent fever. Another naval surgeon, Bryson, later destined to be Medical Director General, in his 'Report on the Climate and Principal Diseases of the African Station (1847)', realized that the outbreaks of fever had nothing to do with lack of cleanliness and improper ventilation of ships, which had formerly been considered factors. Following Lind's precepts he advised:

'If boat services were in some degree restricted, if prize crews were not permitted to land at Sierra Leone, and if all vessels contracting epidemic disease were to leave the station and proceed direct to a cooler climate, the rate of mortality and the permanant loss of health one year with another would be reduced at least nearly a half... No boat shall remain absent over night; were this regulation instituted and adhered to, it is confidently asserted it would do more to reduce the mortality and sickness of the squadron than perhaps all other means of prevention put together.'

The advice of Lind and Bryson is of course as true today as it was then, and is a sheet anchor of naval preventive medicine. But in the Second World War these underlying principles were sometimes forgotten. For instance, at Freetown, when 100 merchant ships were there at one time, in a grossly overcrowded anchorage which favoured mosquito spread, and where normally there were only two or three, there was a high incidence of malaria before full anti-malarial precautions were taken. Now, unfortunately, the use of suppressive anti-malarial drugs, in a similar way as reliance on insecticides against disease-carrying insects, may be a temptation to ignore the principles of prevention, particularly as resistance by living organisms to chemical compounds is an ever growing menace.

Mediterranean or Malta or Undulant fever
In 1814 Burnett, who later became the first Medical Director-General of the Navy, wrote a treatise entitled 'A practical account of the Mediterranean fever as it appeared in the ships and hospitals of HM's Fleet in that station, with cases and dissections.' Though there is some doubt if the disease described by Burnett was in fact true undulant fever, he was the first to use the title 'Mediterranean fever' and his work may be the first published on the disease. Until as late as 1906 Mediterranean fever continued to be a potent source of sickness in the Fleet, when, as the result of Bruce's work, the causal organism was isolated and its mode of propagation through goat's milk recognized. In 1906 their Lordships gave the order 'drink no more goat's milk'; and Mediterranean fever, which since the days of the Crimea had decimated the garrison and fleet stationed at Malta, suddenly ceased within a year.

Yellow fever
In ships operating off the coast of West Africa and South America, yellow fever produced a terrible mortality, and the whisper of 'yellow jack' brought terror to sailors. It was a scourge at Bermuda from time to time until the latter part of the nineteenth century; at the naval hospital 1047 cases were admitted in 1843, and 295 cases in 1864, with a mortality of 22.7 per cent. Bryson described how one of the most distressing features of the disease was the depressing effect on morale, and the spread of the disease had a most demoralizing effect on the ship's company. Convinced that it was contagious, they refused to help nurse the sick, for there were no sick berth staff in those days, and nursing was done by volunteers among the crew. Naval surgeons, to their credit, did not subscribe to the theory of contagion, and the most courageous example in demonstrating this belief was that of Surgeon McKinnal. This is what a brother surgeon wrote of his example:

'To dispel as much as possible the state of general mental depression and convince officers and ship's company that the disease was not contagious, Dr McKinnnal directed me to collect some of the vomit from the first patient who was attacked with that fatal symptom; accordingly, I collected about a pint of it from a man called Riley, I think about two hours before he died. Shortly after this the doctor came up to the starboard side of the half-deck, when I told him what I had done. He went down to the gun room about half past twelve o'clock (the men then being at dinner), returned with a wine glass. Mr. Green, the officer of the forenoon watch, was then going below, when he called him over and filling out a glassful of the black vomit asked him if he would like to have some of it; being answered in the negative, he then said 'Very well, here is your health, Green!' and drunk it off. There were no other persons actually present but those men on duty on the deck at the time, and it became the theme of conversation all over the ship during the afternoon. Dr McKinnal immediately afterwards went to the quarter deck and walked until two o'clock, to prevent it being supposed that he had resorted to any means of counteracting its effects. This took place in February 1830 when the ship was cruising off Lagos, about 180 miles from land.'

The account concluded with the statement:

'It is almost unnecessary to add that it did not impair his appetite for dinner, nor did he suffer any inconvenience from it afterwards.'

McKinnal was not just a brave man demonstrating a belief, but he was also clear-minded - he had noted that the epidemic ceased abruptly upon a certain date, when forty men were on the sick list, and when the power of contagion (if it existed) must surely have been at its height. The prevention of yellow fever was, of course, to follow Lind's and Bryson's advice and anchor well off shore and avoid boatwork up rivers.

Enteric fever and dysenteries
These doubtless produced a high mortality and morbidity, but there is no means of differentiation, as all disorders of this nature were included under the heading of flux. Epidemics of food poisoning, due to inadequate storage of food which was often improperly preserved, were frequent and prostrated whole crews. Decomposed food, provided it could be sufficiently disguised with salt and spices, was not thrown away when there was a short supply. Returns of sickness in those times were headed under fever, flux and scurvy. Later, differentiation was made into fluxes with fever, including dysentery and catarrh; and under nervous diseases were included spasmodic diseases, including diarrhoea, colic, cholera and epilepsy! The true incidence of these diseases is therefore impossible to assess.