Report by Dr WM Aders on Mosquito Surveys at Dar-es-Salaam and in the Kilwa Area
The Mosquito fauna of Dar-es-Salaam, and its environs comprises the following species:-
1. Anopheles costalis
2. Anopheles funestus
3. Anopheles mauritianus
4. Stegomyia fasciata
5. Stegomyia Africana
6. Culex fatigans
7. Culex decans
8. Culex tigripes
9. Ochlerotatus pembaensis
Three of these species are potential disease vectors, viz:
Anopheles costalis and funestus, as malarial carriers; Culex fatigans as vector of Micro-filaria bancrofti (Filariasis). It should be remembered that Stegomyia fasciata is found throughout Dar-es-Salaam. As there are a number of West Africa natives in various camps, the danger of infecting the local Stegomyiae with yellow fever should not be forgotten.
The actual town of Dar-es-Salaam can roughly be divided into three quarters:-
1. The northern end or Garden city.
2. The centre or commercial quarter, from the Kaiserhof to Kaserne.
3. The southern end and suburb of Geresani.
Anophelinae have been found in all three quarters, especially abundant in the southern area, the northern area at the present moment is fairly free, except that numerous anopheline larvae were found in the main drain passing the Remount Camp. In the centre of the town, in the neighbourhood of the Kaiserhof (tends at the side of the hospital) two adult anophelines were captured among many hundreds of Culex fatigans and Stegomyia fasciata. The reason for the presence of these two anophelinae is at present unexplained, the whole area around the Kaiserhof has been most carefully searched but no anopheline larvae found.
On the other hand thousands of culex larvae have been captured in drains, wells, and small pools of foul water. Proceeding further towards the centre of the town, the Boma was investigated. No anopheline were discovered, but again a heavy infection of Culex fatigans.
The southern end of the town is heavily infested with anopheline, the Indian hospital was infected, also four houses on a hill inhabited by Officers belonging to the Union Labour Bureau. The reason for this heavy anopheline infestation is quite obvious. From the south of the Causeway leading to Kurassini, there is a large lake both of its edges being badly swamped (town side and Kurassani side); this area is swarming with anopheline larvae and in my opinion the whole of the southern end of the town up to the Indian hospital is infected from it. It would be an extremely difficult matter to attempt preventative measures in this area considering the nature of the ground and its vast extent. To complicate matters there is also in close proximity a small sluggish stream running down the valley being used as a water supply for various washing establishments. On the land side periphery of the town the situation at the present during the dry season does not seem to be serious; at the end of the Bagamoyo Road there is a small pond surrounded by various wells, etc used by the natives as a washing site. In close proximity is the Infections hospital hardly a salubrious site considering that the above mentioned pond was found to harbour anopheline larvae. The treatment of this area by the use of kerosene would not be a difficult matter, the pond should be cleared of weed and the edge oiled weekly, a few ‘mop-heads’ soaked in oil should be anchored at various points slowly diffusing oil over the area.
The situation in Dar-es-Salaam is as follows:-
The northern and southern ends of the town are infested with anopheline even in the dry season; certain areas on the western periphery are also infected, the centre of the town seems to be almost free and with care should remain so at present. In all probability during the rains and for six weeks afterwards the whole city will be invaded, and considering the large number of susceptible individuals to malaria such as Europeans, Cape Boys, West Indians, etc the infectivity of the anopheline will be greatly enhanced. Undoubtedly many new breeding grounds have been brought into being such as numerous trenches, gun implacements, and shell holes. All such will act as breeding grounds for anopheline.
It will be a difficult and serious problem to combat the situation in the town unless an adequate Mosquito Brigade is formed, even their efforts will in all probability not be able to cope with the situation unless a large number are employed and much kerosene is used.
As regards the various camps, hospitals, etc outside the town area the situation is as follows:-
1. KURASSINI AREA
a) South African Hospital near German Mission
All tents and Cathedral (used as a hospital) were heavily infested with anophelinae. The reason is obvious; on both sides of the hospital are two gorges with small rivulets of water flowing towards the sea. The gorge on the northern side of the camp was formerly used as a vegetable garden, numerous small canals and trenches have been dug for irrigation purposes, on the southern end in close proximity to the well there is likewise a small spring. Both these areas are heavily infected with anopheline larvae. To remedy this an engineer might be consulted as to the advisability of sinking deep wells and collecting the water’ if feasible the well could be easily treated with kerosene. The straightening and cleaning of the edges of the stream and the use of oil might also be considered.
b) Main concentration camp, Kurassani
This area is undoubtedly better than the former, various tents were searched but no anophelinae found. At the edge of the Mangrove Swamp near the main Kurassini well there are a few small streams. Here anopheline larvae were found, also a few suspicious swampy spots just above high water level. Measures could be instituted for eliminating these areas, clean weeding, cutting down bush and regular oiling.
2. GERSANI. SOUTHERN END OF TOWN.
No actual camp has been formed in this area, but there are four small stone bungalows inhabited by European Officers, also a certain number of tents around these houses. The houses are situated in close proximity to a large permanent anopheline swamp.
Nothing could be done in this area without much expense. The houses should be abandoned, but if absolutely necessary should be carefully mosquito-proofed and the occupants warned of their danger.
3. INDIAN HOSPITAL CAMP, NEAR KASERNE.
Anophelinae were found in several tents, probably infected from the above mentioned swamp. No breeding grounds were found in close proximity. It would be advisable to cut down all trees and bush between the hospital and large swamp, so as to make a clean area between the hospital and the swamp. Adult anophelines are not inclined to cross open wind swept spaces.
4. INDIAN DETAIL CAMP.
Numerous anophelinae found in tents, Officers complained that many white NCOs and men went down with fever. Close to the camp there is a sprint and a small stream flowing down a deep nullah. About 200 yards from the spring there is a large swampy area swarming with anopheline larvae (larvae were also found in the spring). The cleaning of this site would be a very difficult matter. Again an engineer might be consulted as to the advisability and possibility of drainage; failing this, the stream should be straightened, cleaned, and at various points large drip cans installed (the latter are cheap and easily constructed).
5. NATIVE DETAIL HOSPITAL.
Situated close to the former and heavily infected with anopheline breeding areas probably the same as the Indian Detail Camp.
6. CARRIER CORPS DEPOT HOSPITAL.
Anophelinae present in Makuti Hospital wards. Near the Camp a small stream running down a valley with a fairly straight course swarming with anopheline larvae. The stream might be treated in the same manner as recommended for the Indian Detail Camp. I was much struck with the Makuti wards and consider that it might be possible to make them mosquito-proof.
7. SIGNAL STATION AREA (ON OPPOSITE SIDE HARBOUR).
In rooms occupied by Naval Units in Signal House no anophelinae were found.
One pool near coal shack was swarming with anopheline larvae; it could be easily filled in. According to German reports this site had in former years a most evil reputation.
The area might remain under consideration for a Camp.
8. ARTILLERY DEPOT (ON MAIN CREEK NEAR WRECKED TABORA).
At foot of cliff under main buildings long swampy area at present small in extent but would be probably much increased during the rains. Reported by Germans as most malarious.
9. REMOUNT CAMP (NEAR TENNIS COURTS).
Main drain was found blocked, infested with anopheline larvae. Probably all this northern area in the rains will be one vast anopheline breeding ground; I am given to understand from German records that the greater part is planted with rice.
Situation safe in dry season, very dangerous in the rain.
10. IMPERIAL DETAIL CAMP.
Numerous anophelines found in tents, Officers complained that many men went down with fever. One small pool was fond at edge of Mangrove Swamp, containing anopheline larvae, could be easily filled in. The other side of the camp is not very far from the pond at the end of Bagamoyo Street, near Infectious hospital, and will be probably worse in the rains and very difficult to tackle.
From the above evidence it is clear that all the camps situated around the town of Dar-es-Salaam are infected with anophelinae. In all instances, I feel sure it will be extremely difficult to eliminate the breeding grounds; the situation during the rains and for six weeks afterwards will be far worse.
I suggest that a small Mosquito Brigade be formed in each camp and hospital; as most of the breeding sites are now known it would be possible to exercise some control. A Mosquito Brigade consisting of native boys, who are easily trained in collecting adults and larvae, should be started. Each gang should work in a definite quarter of the town, reporting daily to OC No 9 Sanitary Section where larvae have been found. The OC Sanitary Section could then personally inspect the site and decide as to control methods, filling in, oiling, draining, etc. With a very small number of men, many small areas would probably be detected and perhaps eliminated. If this method proved efficacious it might be extended to the various detail camps. The cost of such a brigade would be very small.
Much can be done in eliminating mosquito larvae by simple easy methods such as:-
1. Cleaning the edges of streams of weeds.
2. Straightening streams’ courses, and trimming edges with stone.
3. Oil: applied either by spraying, drip cans, anchored oil mops etc.
4. Diversion of water into dug-holes, etc and the latter treated with oil.
5. In the town area the dominant mosquito is Culex fatigans; the larvae of this species are nearly always found in foul water and they show a marked partiality for cess pools, drains, etc.
If Householders could be induced to oil all drains weekly through the bath water down pipe, this troublesome pest would be enormously reduced. Many of the wells in the town also contain larvae. These should be systematically oiled (practically no taste of oil is imparted to the water).
Major Hume Patterson accompanied me to all the sites visited and I should like to express my thanks to him in affording me every facility for carrying on my work.
I have the honour to be, Sir
Your obedient servant, (sgd) WM Aders
Report by Dr Aders on the Sanitary conditions at Kilwa
Dated 22 April 1917
On arrival at Kilwa I at once reported to Lieut-Colonel Manifold, RAMC, and discussed with him a scheme of investigation re the presence and distribution of Anophelines in Kilwa Kivinji and its surroundings.
The following programme was drawn up:-
1. The presence of anophelinae in the Hospital.
2. Investigation of all breeding places of anopheline larvae in close proximity to the hospital (Stationary Hospital No 19).
3. Investigation of the Carrier Corps Camp and Hospital.
4. Presence of anophelinae on Red Hill.
5. Presence of anophelinae at Mpara.
6. Presence of anophelinae at Kilwa Kisiwani.
The presence of anophelinae and distribution of larvae in:-
HOSPITAL AREA AT KILWA KIVINJI.
Adult anophelines (A. costalis and mautitanus) were found in considerable numbers throughout the various wards and hospital tents among them great numbers of Culex fatigans and a few Stegomyia fasciata.
Anopheline larvae were found in a swampy patch facing the main entrance to the hospital in considerable numbers. The area around the Officers’ Quarters is one huge swamp breeding countless numbers of larvae. In my opinion no preventive measures could be taken in this are without a large sanitary staff and great expenditure.
I recommend that some pools in close proximity to the hospital should be drained or oiled but considering the enormous area of the marshy ground no great amelioration of the existing conditions can be expected. The river which flows into the sea near the hospital is, for a great distance tidal, here I was unable to find any anopheline larvae; a few Ochlerotatus pembaensis were found in crab-holes on the banks.
THE CARRIER CORPS CAMP AND HOSPITAL.
The camp is situated at some distance from the Stationary Hospital towards the south of the town. Here likewise many adult anophelinae were found in the various tents and buildings searched. A large shallow swamp was found within a few hundred yards from the camp breeding great numbers of anopheline larvae. The camp is surrounded on two sides by a mangrove creek; in the southern creek situated a considerable distance from the buildings a few pools containing a large amount of fresh water harboured larvae. This site is undoubtedly a preferable one to that occupied by the Stationary Hospital. Throughout the town there are numerous large flooded areas breeding enormous numbers of anophelinae.
The whole plain stretching from the two to its base is one vast swampy area, intersected by numerous streams, all of which are probably permanent. On the slopes of the hill many springs and small rivulets with marshy banks exist; all contain anopheline larvae (the majority were A funestus, a most virulent malarial carrier).
Tents occupied by the various Tram-Line Officials harboured anophelines. The crest of the hill is dry but on the western slope there is a stream of some size. Here again larvae were found. Lieut-Col Manifold informed me that while the North Lancs were encamped on the crest many were taken sick with a most virulent type of fever.
Is situated seven miles from Kilwa Kivinji on the main road to Kilwa Kisiwani. A large areas of ground has been cleared and bandas erected. On the northern slope of the encampment is a large stream coming from hills about 2 to 3 miles away. The whole of the area watered by this stream is badly swamped much of which will eventually dry; the conrol of the stream without considerable engineering works would be almost impossible. The tents and bandas contained anophelines and larvae were found in the above described swamp.
Undoubtedly the best site. In the Hospital few anophelinae were found; larvae were discovered in a few pools, these could be easily treated. An excellent site at the point facing the entrance to the harbour is at present occupied by Naval Officers. In conjunction with Colonel Manifod a most careful examination was made of the situation. Adult anophelines were found in the tents and bandas, their breeding places are all in close proximity and not of any great extent, most of them small pools on the foreshore and a few rock pools on the cliff. After the clearing of the site it should be easy to trace all these small breeding areas, and treat them by filling in, draining or oiling.
To sum up the situation:-
Kilwa Kivinji is at present moment one vast swamp, impossible to deal with. In all probability even in the driest season numerous breeding grounds for anophelinae will still exist.
Red Hill. Numerous permament springs and rivulets are present abounding with larvae of A. funestus. A most unsuitable site for a permanent Stationary Hospital.
Mpara. Likewise unsuitable, as the stream will in places always breed anophelines.
Kilwa Kisiwani. By far the best situation. The site at the entrance to the harbour could be easily controlled as far as anophelines are concerned.
At your request I examined the three sites for other disease carrying anthropods with a negative result, except that a species of Culicoides was prevalent on Red Hill. This genus is not known as yet to carry disease.
Ornithodorus moubala was not ound on any of the sites inspected.
Lieut-Colonel Manifold accompanied me to all the sites visited and I should like to express my thanks to him for affording me every facility for carrying on my work.
(sgd) WM Aders