Writings on Malaria |
Introduction
Cyclical Spraying Operations on Choiseul Island commenced in September 1968 and have since been carried out at regular six-month intervals Surveillance operations were launched in early 1971 and covered the whole island by mid-1971. 1972 was thus the first full year of surveillance operations. The Regional Headquarters are at Susuka covering Zones 44, 45, 46 and 47; and Malanagono covering Zones 41, 42, 48 and 49. Wagina, Zone 43 (the home of people resettled from the Gilbert Islands and, hence, with no prior exposure to malaria), is supervised directly from District HQ at Gizo.
Slide collection has in general been good throughout the year although in some zones there have been months in which no slides have been collected by Active Case Detection (ACD, by MEP Epidemiology technicians making scheduled visitis to villages) notably in January, February, June, October (ACD) and November in Zone 45, in February and November (ACD) in Zone 47, November in Zone 49, July in Zone 42, and February in Zone 44. Passive Case Detection (PCD) activities (bloodslides taken at local health clinics) usually fluctuate considerably but these have not been analysed in detail.
Records
| (a) | The zone maps, as produced by the Geographical Reconnaisance (GR) Section and based on information received from the Cyclical Spraying staff, show a total of some 330 villages. The Epidemiology village records system at the start of my study had cards for some 204 of these villages. The majority of the other 126 villages turned out, on examination of the G.R. spray record cards, to be of no more than one or two houses and often of the garden house, copra-house type of structure, ie, with no permanent population. |
| (b) | There were, however, 112 epidemiology record cards which related to villages in a different zone to that shown on the card. The extreme example was Huatambu, Zone 44, which had record cards with five separate zone numbers. Vurago, Nukiki and Voza each appeared on four separate cards. The reason for this multiplication would appear to be simple misnumbering by ACD technicians; simple misnumbering by PCD agents; use of a single General Purpose Form for more than one zone; and, collection of slides from visitors to the village where the slide was taken but with the name of the home village given. |
| (c) | After careful scrutiny of both epidemiology and GR records I was able to correctly allocate many of the cards but ended up with some 38 cards naming villages at which slides had not been collected in recent months but which do not appear either on the maps or in the spray records (the most recent spray cycle was June-July 1972). |
| (d) | A gratifying note was that 108 cases were detected between January and November 1972, not including Wagina, Zone 43, according to the monthly MTOC Annex 1, and all 108 of these appear on the village record cards. However, the misrecording indicated in paragraph (b) above has led to the zonal distribution of cases being incorrectly reported in the MTOC Annex viz the following table: |
| Case distribution | MTOC Annex | Corrected Record |
| Zone 41 | 1 | 0 |
| Zone 42 | 0 | 1 |
| Zone 44 | 5 | 8 |
| Zone 45 | 4 | 1 |
| Zone 46 | 52 | 50 |
| Zone 47 | 23 | 22 |
| Zone 48 | 21 | 25 |
| Zone 49 | 2 | 1 |
| Total | 108 | 108 |
No doubt the numbers of slides collected per zone, as in the MTOC Annex, has also been given incorrectly but to correct this would be an extremely time consuming exercise. The total for the island should be correct to within a small number.
Positive Cases
As has already been noted, there were 108 cases between 1st January and 30th November from Choiseul Island, thus not including Wagina, The majority of those cases were at the north-western end of the island in Zones 46, 47 and 48 with 82 cases in the area between Vuruvuru, in the east, and Poro Poro, in the west. The remaining 21 cases were scattered but 15 were on the north coast. The anomaly in numbers, i.e. 103 cases plotted on the map, is due to a number of relapses, which appear in the records as new case each time but I have not repeated them on the map (see below, the map also shows December cases).
Wagina has been the subject of an intensive campaign including Mass Drug Administration and I am not going to deal further with it except to say there were 156 cases of vivax prior to September since then there have been 9 in September, 1 in October and 2 in December.
All cases for which investigation results are recorded (54) were indigenous to the island or else were relapses.
Plasmodium malariae
There were only three cases on mainland Choiseul and two on Wagina during 1972. One of them was in one of the few bush villages on the island and the other two were in the north coast epidemic area.
Plasmodium vivax
The most disturbing feature of the vivax cases is the fairly high number of relapses amongst small children. Typical of these were:
| i. | At Ogo, Zone 46, Karavavini (a) Eddina, age 1, detected 21.7.72 as a house contact and again detected on 1.8.72 as a PCD case. CFU (Case Follow Up) slides were taken on 3.11.72 and 21.11.72, both were Positive. (b) Harryson Pupujuku, age 2, also detected 21.7.72 as a house contact. CFU slides on 21.11.72 and 19.12.72 both were Positive. |
| ii. | At Polo, Zone 46, Slim Dusty, age 1, was detected on 17.1.92 by a PCD agent and classified as a relapse (possibly this was erroneous). On 18.2.72 a CFU slide for Slim now aged 8/12 was Positive. |
| iii. | At Saelae, Zone 46, a CFU slide from Emelder Qulovavini, aged 3/12 was Positive on 14.6.72. Further slides from Emelder on 22.11.72 and 6.12.72 also were Positive. |
| iv. | At Susuka, Zone 46, Jennifer Daekolo was Positive on 8.11.71 and a CFU slide on 3.11.72 also was Positive. |
| v. | At Voro Voro, Zone 46, Nicholas Samelesolomo, aged 2, was found Positive on 12.4.72 and on 3,10.72 still was Positive. |
| vi. | At Salakana, Zone 48, Caleb Kukuta, age 7, still was Positive on 18.1.72 having been detected in an MBS (Mass Blood Survey) on 22.2.71. |
| vii. | At Sibesibe, Zone 48, Elen Saraneseko, aged 2, was detected first on 12.5.71 and still was Positive on 25.1.72. |
Of the 70 cases of vivax detected in 1972 only 14 were aged over 9 years.
Plasmodium falciparum
F237, F327, etc. are simple falciparum parasite levels in blood slide examinations; Fg200, etc., indicates levels of gametocytes (infectious stages); V3 etc., indicate vivax levels.
| 1. | Some 19 cases were detected in 1971 and 31 in 1972, of these 17 were detected by PCD agents and 24 were gametocyte carriers (12 in each of the two years). Only 19 of the patients were aged over 9 years old. The case distribution is plotted on the map. |
| 2. | Several patients appear more than once in our records, they are: (a) At Poroporo, Zone 48, Benjamin, age 9, slide taken 22.6.71 by PCD, F237. Benjamin, age 9, slide taken 1.6.72 by PCD, F327. (b) At Sibesibe, Zone 48, i. Peter Lokasava, age 4, slide taken 12.5.71, F500 Fg200. Peter Lokasava, age 4, slide taken 9.2.72 (CFU slide) V3. ii. Keven Velokaevo age 5, slide taken 12,5,71, Fg10. Keven Velokaevo, age 5, slide taken 10.11.72 (CFU slide) V2. (c) At Chivoki, Zone 47, Gotman Zele, age 1, slide taken 23.8.72, F132. Gotman Zele, age 1, slide taken 12.9.72, F9. (d) At Sirondona, Zone 47 i. Joseph Karomae, age 3, slide taken 15.2.71 by PCD, F+++. Joseph Karomae, age 3, slide taken 10.5.71, F25 Fg. (in a 21.2.71 MBS at Vurago, Joseph Koronai, age 3 was Fg314). ii. Paul Batogo, age 2 1/2, slide taken 21.9.71, F44. Paul Batogo, age 2 1/2, slide taken 17.11.11 (CFU slide) Fg61. (in a 21.2.71 MBS at Vurago, Paul Batogo, age 2, was V91). (e) At Vurago, Zone 47, S. Turianava, age 8, slide taken 26.3.72 by PCD, F260. S. Turianava, age 8, slide taken 30.10.71 (CFU slide) V1. (f) At Voruvoru, Zone 46, Lawrence Rirotita, age 2, slide taken 12.4.72 by PCD, V140 Lawrence Rirotita, age 2, slide taken 20.10.72 (CFU slide) F17. The appearance of a low level infection of vivax in the CFU
slide, as in three of these patients, is not entirely surprising as a
falciparum infection will tend to mask a vivax
infection. |
| 3. | The sporadic nature of the detection of cases and the scattered
distribution of the cases leads me to wonder whether the surveillance
mechanism is picking up all the cases or if there is a continuous low
level reservoir of the parasite in the community. The fact that about
60% of the cases detected are children under 9 years of age would
suggest that it is the adults which form this reservoir (7 out of the 19
adults were gametocyte carriers). The earliest case detected In the 1972
epidemic at Poro Poro was an adult on 2nd May with Fg26. The next case
was detected on 26th May, followed in succession by cases on 1st June -
two, 4th June, 5th June, 14th June and 16th June (the 26th May to 5th
June cases were detected by a PCD agent). No further cases have been detected at Poro Poro but the cases at Sipukana and LiuLiu in June (three cases, the first of which, F108 Fg49, was on 6th June and the other two on 19th June) and Saga Saga in October seem likely to have originated in Poro Poro. |
Dr. B. Taylor
Government Entomologist
30.1.73
| ©1999 - Brian Taylor CBiol FIBiol
FRES 11, Grazingfield, Wilford, Nottingham, NG11 7FN, U.K. Visiting Academic in the Department of Life Science, University of Nottingham Comments to dr.brian.taylor@ntlworld.com |
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