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Filariasis in the Cameroon
418 TRANSACTIONS OF TICS ROYAL SOCIETY OF TROPICAL MEDICINE AND HYGIENE. VoI. X X I . No. 5. February, 1928.
FILARIASIS
IN T H E
CAMEROON,
W I T H S P E C I A L R E F E R E N C E T O S K I N I N F E C T I O N S BY MICROFILARIzZE. BY N. A. DYCE
SHARP, M.R,C.S., L.R.C.P.
West African Medical Service, Nigeria.
Of that portion of the Cameroon which is held under mandate by the British Government, the southern and larger half is covered by dense forest and intersected by numerous streams, flowing perennially owing to the prolonged rainy season. Here the natives live in tiny scattered villages, where they maintain a perpetual war against the ever-invading growth of dense thicket. In two years a deserted farm will revert to impenetrable bush, the so-called secondary bush, which is far heavier and denser than the natural undergrowth of virgin forest. While the latter provides but scanty cover for the majority of biting flies, secondary bush produces an environment exactly suited to the needs of such inseets as simulium and ehrysops, as well as of the little midge culicoides. The Mature division of the Cameroon is about 6,000 square miles in area, and holds a population of 63,000 persons, one-third of whom live at an altitude of 3,000 to 6,000 feet. Here the climatic conditions are different, for the forest has given way to low orchard scrub or open grass land, and the streams are torrential and tend to dry up after the rains. These remarks are of importance in view of the fact that this particular district is perhaps the most heavily infected with filaria of any in the world. Filaria bancrofti, it is true, is absent or nearly so, butLoa loa, Acanthocheilonema perstans and Onchocerca volvulus, together with the little embryo described by MACFIE and CORSON, a r e excessively prevalent.
Microfilari~e Infecting the Blood. GRIEVE made, in 1924, an extensive investigation into the incidence of infection by L. loa and A. perstans, and found that the percentage of population infected with L. loa was 17, with A. perstans 77, and with F. bancrofti only 0"4.
414
FILARIASIS IN TItE CAMEROON.
The writer's figures, which, however, are based on a far smaller total of cases examined, do not include natives from the hilly country. They are as follows : L. loa : infection rate, 6 per cent. (of 50 men examined at 9 p.m.). A. perstans: infection rate, 92 per cent. F. bancrofti : infection rate, 2 per cent. (of 50 men examined at 9 p.m.). These figures clearly show that the adult population is subject to a very high degree of parasitism by filari~e of little known pathogenicity. Such an infestation cannot be said to account for the " C 3 " condition of the bulk of the population, but it seems difficult to exclude it as an accessory factor.
Mierofilarice Infecting the Skin. During the past eighteen months the incidence of infection of the skin with filarial embryos has been made the subject of a special investigation, and portions of skin have been removed from 100 adult males, 34 adult females, 30 boys between the ages of 6 and 16, and 30 girls between 8 and 16. The examination was conducted as follows :-T h e skin over the left lumbar muscle was cleaned with spirit and then injected with 1 c.cm. of stovaine and adrenalin (in the absence of novocaine which is more efficient) so as to raise a plaque of skin the size of a sixpence. T h i s plaque was then shaved off with a safety razor blade and the fragment of skin placed on a slide in saline and at once examined. Usually it was necessary to cut the skin into smaller fragments and occasionally to wait five minutes. T h e differential diagnosis was clinched by subsequent staining. Apart from the prick of the needle the operation was painless, and even the children made no objection to it, though their parents were inclined to on their behalf.
The results are shown below in the Tables I to III. TABLE I. Class.
Men ......
Women
Boys . . . . . . Girls . . . . . .
...
No. examined.
No. showing embryos of O. volvulus.
100 34 30 30
95 33 26 16
I
Percentage.
95 97 87 53
In the case of O. volvulus, the incidence of infection is even higher than that showed by the blood microfilarim ; the rate, indeed, is amazing. At the same time the little filarial embryo called by MACFIE and CORSON (1921) Agamofilaria streptocerca, was sought for and found in a large number of cases, details of which are given in Table II.
4t5
N. A. DYCE SHARP. TABLE I I . Class.
No. examined.
No. s h o w i n g
Percentage.
.4. streptocerca. Men ...... Women Boys . . . . . . Girls . . . . . .
80 34 30 30
...
32 13 3 0
40 38'3 10 0
This little orphan embryo, whose parents have yet to be discovered, is considered by MANSON-BAItR to be allied to O. volvulus and, although there are excellent grounds for believing that it is a separate species, it will be convenient to treat the two types for statistical purposes, as merely skin filari~e. In Table I I I the combined figures are given, and this Table shows the total incidence of infection of the skin of the cases uru:ler review. TABLE
No. e x a m i n e d .
Class.
Men
. . . . . .
Women Boys . . . . . . Girls . . . . . .
...
..°
,°.
100 34 30 30
III.
N o. s h o w i n g skin infection w i t h filarial embryos. 97 33 29 16
Percentage.
97 97 96"3 53"3
Almost all the men were prisoners drawn from all parts of the division ; the three negative cases came from villages at heights of 3,000, 4,000 and 4,500 feet above sea level. The women were chiefly drawn from villages within 20 miles of Mamfe station, that is to say, from the dense forest region. It was unfortunate that the one negative case could not be re-examined. The boys were drawn from the same area and were all school boys. Two aged 11 and one aged 13 showed volvulus tumours, one of the former being a leper. All the three boys who exhibited the agamofilaria came from the same village, Besongabang, as did three out of the thirteen women infected. In this village it should not be difficult to find the vector of this little parasite. The youngest infected boy was aged 8 ; he exhibited the agamofilaria only. The most massive infection was in a boy aged 9, with O. volvulus. The girls were all drawn from villages within twenty miles of Mamfe station. The youngest found infected with O. volvulus was a child of 8, while a little girl of 10, who was also positive, had three volvulus tumours on her chest
416
FILARIASIS IN THE CAMEROON.
wall. Another child of the same age complained of extreme irritation of the skin always at the full moon, while another, 13 years of age, was not only a leper, but showed a heavy blood infection with embryos of A . perstans. It is probable that, from faulty technique or from failure to secure a portion of skin which happened to be infected, some cases have been missed, and one can, therefore, assert with considerable confidence that every adult native of the forest portion of the Cameroon is infected with O. volvulus or with its junior colleague described by MACFIE. Such a condition of parasitism is probably without parallel in any part of the globe, and it envisages a problem in preventive medicine and practical therapeutics which demands most careful and prolonged investigation if the filarial infection of this " C 3 " population is to be ameliorated. It was not uncommon to find a boy or girl under 16 showing a simultaneous infection with leprosy, yaws, O. volvulus, and A . perstan~
FILARIASIS
IN T H E
CAMEROON,
W I T H S P E C I A L R E F E R E N C E T O S K I N I N F E C T I O N S BY MICROFILARIzZE. BY N. A. DYCE
SHARP, M.R,C.S., L.R.C.P.
West African Medical Service, Nigeria.
Of that portion of the Cameroon which is held under mandate by the British Government, the southern and larger half is covered by dense forest and intersected by numerous streams, flowing perennially owing to the prolonged rainy season. Here the natives live in tiny scattered villages, where they maintain a perpetual war against the ever-invading growth of dense thicket. In two years a deserted farm will revert to impenetrable bush, the so-called secondary bush, which is far heavier and denser than the natural undergrowth of virgin forest. While the latter provides but scanty cover for the majority of biting flies, secondary bush produces an environment exactly suited to the needs of such inseets as simulium and ehrysops, as well as of the little midge culicoides. The Mature division of the Cameroon is about 6,000 square miles in area, and holds a population of 63,000 persons, one-third of whom live at an altitude of 3,000 to 6,000 feet. Here the climatic conditions are different, for the forest has given way to low orchard scrub or open grass land, and the streams are torrential and tend to dry up after the rains. These remarks are of importance in view of the fact that this particular district is perhaps the most heavily infected with filaria of any in the world. Filaria bancrofti, it is true, is absent or nearly so, butLoa loa, Acanthocheilonema perstans and Onchocerca volvulus, together with the little embryo described by MACFIE and CORSON, a r e excessively prevalent.
Microfilari~e Infecting the Blood. GRIEVE made, in 1924, an extensive investigation into the incidence of infection by L. loa and A. perstans, and found that the percentage of population infected with L. loa was 17, with A. perstans 77, and with F. bancrofti only 0"4.
414
FILARIASIS IN TItE CAMEROON.
The writer's figures, which, however, are based on a far smaller total of cases examined, do not include natives from the hilly country. They are as follows : L. loa : infection rate, 6 per cent. (of 50 men examined at 9 p.m.). A. perstans: infection rate, 92 per cent. F. bancrofti : infection rate, 2 per cent. (of 50 men examined at 9 p.m.). These figures clearly show that the adult population is subject to a very high degree of parasitism by filari~e of little known pathogenicity. Such an infestation cannot be said to account for the " C 3 " condition of the bulk of the population, but it seems difficult to exclude it as an accessory factor.
Mierofilarice Infecting the Skin. During the past eighteen months the incidence of infection of the skin with filarial embryos has been made the subject of a special investigation, and portions of skin have been removed from 100 adult males, 34 adult females, 30 boys between the ages of 6 and 16, and 30 girls between 8 and 16. The examination was conducted as follows :-T h e skin over the left lumbar muscle was cleaned with spirit and then injected with 1 c.cm. of stovaine and adrenalin (in the absence of novocaine which is more efficient) so as to raise a plaque of skin the size of a sixpence. T h i s plaque was then shaved off with a safety razor blade and the fragment of skin placed on a slide in saline and at once examined. Usually it was necessary to cut the skin into smaller fragments and occasionally to wait five minutes. T h e differential diagnosis was clinched by subsequent staining. Apart from the prick of the needle the operation was painless, and even the children made no objection to it, though their parents were inclined to on their behalf.
The results are shown below in the Tables I to III. TABLE I. Class.
Men ......
Women
Boys . . . . . . Girls . . . . . .
...
No. examined.
No. showing embryos of O. volvulus.
100 34 30 30
95 33 26 16
I
Percentage.
95 97 87 53
In the case of O. volvulus, the incidence of infection is even higher than that showed by the blood microfilarim ; the rate, indeed, is amazing. At the same time the little filarial embryo called by MACFIE and CORSON (1921) Agamofilaria streptocerca, was sought for and found in a large number of cases, details of which are given in Table II.
4t5
N. A. DYCE SHARP. TABLE I I . Class.
No. examined.
No. s h o w i n g
Percentage.
.4. streptocerca. Men ...... Women Boys . . . . . . Girls . . . . . .
80 34 30 30
...
32 13 3 0
40 38'3 10 0
This little orphan embryo, whose parents have yet to be discovered, is considered by MANSON-BAItR to be allied to O. volvulus and, although there are excellent grounds for believing that it is a separate species, it will be convenient to treat the two types for statistical purposes, as merely skin filari~e. In Table I I I the combined figures are given, and this Table shows the total incidence of infection of the skin of the cases uru:ler review. TABLE
No. e x a m i n e d .
Class.
Men
. . . . . .
Women Boys . . . . . . Girls . . . . . .
...
..°
,°.
100 34 30 30
III.
N o. s h o w i n g skin infection w i t h filarial embryos. 97 33 29 16
Percentage.
97 97 96"3 53"3
Almost all the men were prisoners drawn from all parts of the division ; the three negative cases came from villages at heights of 3,000, 4,000 and 4,500 feet above sea level. The women were chiefly drawn from villages within 20 miles of Mamfe station, that is to say, from the dense forest region. It was unfortunate that the one negative case could not be re-examined. The boys were drawn from the same area and were all school boys. Two aged 11 and one aged 13 showed volvulus tumours, one of the former being a leper. All the three boys who exhibited the agamofilaria came from the same village, Besongabang, as did three out of the thirteen women infected. In this village it should not be difficult to find the vector of this little parasite. The youngest infected boy was aged 8 ; he exhibited the agamofilaria only. The most massive infection was in a boy aged 9, with O. volvulus. The girls were all drawn from villages within twenty miles of Mamfe station. The youngest found infected with O. volvulus was a child of 8, while a little girl of 10, who was also positive, had three volvulus tumours on her chest
416
FILARIASIS IN THE CAMEROON.
wall. Another child of the same age complained of extreme irritation of the skin always at the full moon, while another, 13 years of age, was not only a leper, but showed a heavy blood infection with embryos of A . perstans. It is probable that, from faulty technique or from failure to secure a portion of skin which happened to be infected, some cases have been missed, and one can, therefore, assert with considerable confidence that every adult native of the forest portion of the Cameroon is infected with O. volvulus or with its junior colleague described by MACFIE. Such a condition of parasitism is probably without parallel in any part of the globe, and it envisages a problem in preventive medicine and practical therapeutics which demands most careful and prolonged investigation if the filarial infection of this " C 3 " population is to be ameliorated. It was not uncommon to find a boy or girl under 16 showing a simultaneous infection with leprosy, yaws, O. volvulus, and A . perstan~