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Keywords:

  • malaria;
  • filariasis;
  • concomitant infections;
  • prevalence;
  • Guyana

Summary

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results
  6. Nocturnal survey
  7. Diurnal survey
  8. Discussion
  9. Acknowledgements
  10. References

Lymphatic filariasis and malaria are endemic in Guyana, South America. To determine the prevalence of concomitant infections, we conducted a 1-year survey of febrile patients attending the malaria (day) and filariasis (night) clinics in Georgetown. In all, 1278 thick blood smears were collected: 769 for filariasis, of which 103 were positive for Wuchereria bancrofti, and three for both W. bancrofti and malaria parasites; and 509 for malaria, 21 of which tested positive for malaria and 17 for both malaria and filariasis. The age groups and sex of the infected persons with malaria and W. bancrofti are described. These results suggest that the incidence of concomitant infections in Guyana may be quite low but efforts should be made to reduce the disease burden in Georgetown, Guyana.


Introduction

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results
  6. Nocturnal survey
  7. Diurnal survey
  8. Discussion
  9. Acknowledgements
  10. References

Malaria and filariasis are the two major mosquito-borne public health diseases transmitted in South America (Giglioli 1948; Hawkings 1979; Nathan & Stroom 1990). In Guyana, Plasmodium falciparum and P. vivax are the prevalent malaria parasite species responsible for over 35 000 cases annually (Chadee 1998). Filariasis caused by the microfilariae Wuchereria bancrofti and Mansonella perstans causes more than 8000 cases annually in the capital city of Georgetown (Nathan & Stroom 1990; Rawlins et al. 1999), with the latter species being insignificant in the pathology of the disease (Chadee et al. 1995).

In many areas endemic for lymphatic filariasis, infections with other blood-borne parasites are common. Several reports have indicated that a high incidence of malaria and filarial blood-borne parasites exists among the human population within South America. Therefore, concomitant parasitism should be a fairly common feature but no reports have been found documenting the existence of this feature, although extensive surveys are conducted annually at the Malaria and Filaria Clinics in Georgetown, Guyana. This is the first report on malaria and filariasis coinfections in Guyana. The data from this study may be useful to future workers considering mass chemotherapy for either malaria or filariasis.

Materials and methods

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results
  6. Nocturnal survey
  7. Diurnal survey
  8. Discussion
  9. Acknowledgements
  10. References

Over the period January–December 1997 all patients from Guyana visiting the Georgetown Malaria and Filariasis Clinics were enrolled in the study. Informed consent was obtained both verbally and in writing from each patient participating in this study. Nocturnal thick blood smears were prepared using approximately 20 mm3 of blood taken between 8 pm and 12 am, dried and stored overnight. This time period of blood collection was chosen because of the nocturnal periodicity of W. bancrofti (Nathan & Stroom 1990). For the diurnal study, we took samples from all febrile patients attending the Malaria Clinic between 8.30 am and 4 pm. Slides were stained using the standard Giemsa protocol and microscopically examined for the presence of microfilariae and malaria parasites. All positive microfilariae and malaria smears and 15% of the negative smears were re-examined. All personal data were recorded on standard forms that included age, sex, ethnic origin and home address.

Data were analysed by transformation into contingency tables and subjected to a G-test (Petrie & Sabin 2000) to determine the differences in distribution and infestation levels among the different age groups infected with malaria and filariasis in Guyana.

Results

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results
  6. Nocturnal survey
  7. Diurnal survey
  8. Discussion
  9. Acknowledgements
  10. References

From a total of 1278 blood smears taken, 83% were African, 10% were East Indians and 7% were mixed or of other ethnic origins. Of the 1278 smears collected, 769 (386 males and 383 females) were taken during nocturnal hours at the Filariasis Clinic whereas 509 smears (349 males and 160 females) were obtained during diurnal hours at the Malaria Clinic in Georgetown, Guyana.

Nocturnal survey

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results
  6. Nocturnal survey
  7. Diurnal survey
  8. Discussion
  9. Acknowledgements
  10. References

Of the 769 blood smears collected, 103 were found positive for W. bancrofti monoinfection and three for mixed infections with W. bancrofti and malaria parasites (one case with P. vivax and two cases with P. falciparum). Of the 103 positive smears, 79 were from individuals of African origin, 14 of East Indian origin, four of Caucasian origin, three of mixed heritage and three of Native American origin.

The distribution of microfilariae according to age and sex is given in Table 1. The youngest infected person was a 5-year-old child. The prevalence of W. bancrofti increased with age, peaking in the 20–39-year age group, where the overall prevalence was 41.7% (G = 32.1, d.f. = 5, P > 0.001). In the older age groups the prevalence ranged from 7.8% to 24.3%. The overall rates for the two sexes were significantly different (G = 24.9, d.f. = 1, P > 0.001) with 63.1% for males and 36.9% for females.

Table 1.  The prevalence of Wuchereria bancrofti infections among different age groups and sexes visiting the Georgetown Filariasis Clinic during nocturnal hours from January to December 1997
Age groupsNo. of smearedNo. of infected
MalesFemalesTotalMales (%)Females (%)Total (%)
  • *

    Mixed infection.

0–4000000
5–93419532 (5.9)1 (5.3)3 (5.7)
10–1943388112 (30.0)12 (31.6)24 (29.6)
20–3910110720834* (33.7)9 (8.4)43 (20.7)
40–5917317935214 (8.1)11 (13.9)25 (7.1)
> 603540753 (8.6)5 (12.5)8 (10.7)
Total38638376965 (16.8)38 (9.9)103 (13.4)

Diurnal survey

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results
  6. Nocturnal survey
  7. Diurnal survey
  8. Discussion
  9. Acknowledgements
  10. References

Of the 509 blood smears collected, 21 were from individuals with malaria monoinfection and 17 from people infected with both malaria and microfilaria parasites (Table 2). Mansonella perstans, a filarial parasite known to occur in some inland communities, was found in a female Amerindian living on East Coast Demerara; all other filarial parasites detected were identified as W. bancrofti, with one case being infected with three different parasite species (Table 2).

Table 2.  Prevalence of malaria parasitaemia and Wuchereria bancrofti microfilariae in four townships in Guyana (1997)
TownsNo. of smears examinedPositive for malariaPositive for P. vivax and W. bancroftiPositive for P. falciparum and W. bancroftiTotal positive for malaria and W. bancrofti
  • *

    One case of M. perstans and P. vivax.

  • **One case of P. vivax, P. falciparum and W. bancrofti.

Kitty1304011
East Bank Essiquibo1215033
Georgetown1354145
East Bank Demerara1238257**
Total5092131417*

Of the 17 cases with concomitant infections, a significant number (G = 22.98, d.f. = 5, P > 0.01) or 16 (94.1%) were males with more than 50% representing the 20–39-year age group and followed by the 10–19-year age group (35.3%). No mixed infections were observed among children up to age 9 (Table 3).

Table 3.  The prevalence of Plasmodium falciparum and/or Plasmodium vivax infection among different age groups and sexes visiting the Georgetown Malaria Clinic during the diurnal study from January to December 1997
Age groupsNo. of smearedNo. of infected
MalesFemalesTotalMales (%)Females (%)Total (%)
  • *

    Mixed infection.

  • 21 cases of only malaria infections (17 P. falciparum and four P. vivax cases).

0–4000000
5–9191635000
10–193915545 (12.8)1* (6.7)6 (11.1)
20–3983551389 (10.8)09 6.5)
40–59171582292 (1.2)02 (0.8)
>603716530 (0)00
Total34916050916 (4.6)1 (0.6)17 (3.3)

Discussion

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results
  6. Nocturnal survey
  7. Diurnal survey
  8. Discussion
  9. Acknowledgements
  10. References

Although numerous microfilariae and malaria surveys were conducted in Guyana between 1896 and 1990 (Giglioli 1948; Nathan & Stroom 1990), little or no information is available on the incidence of concomitant infections (of malaria and filariasis); only information on microfilariae carriers during malaria surveys on both the coast and in the interior of Guyana was available. Thus the 20 cases of malaria and bancroftian filariasis we found may be the first documentation of the occurrence and prevalence of this phenomenon in Guyana.

In a recent review, Chadee (1998) reported an incidence of 5% (35 000 cases in a population of 750 000) malaria in Guyana while Nathan and Stroom (1990) reported an incidence of 6.5% filariasis among the Georgetown population, the capital city of Guyana. Therefore, the coinfection of malaria and filariasis raises an important issue relating to early diagnosis of filariasis, as the symptoms of filariasis do not rapidly appear within 7–10 days after infection, as is the case in malaria, and would not normally be diagnosed prior to onset of symptoms. These results suggest that laboratory technologists should be trained to differentiate between malaria and microfilaria parasites. At present the malaria and filariasis laboratories in Georgetown are run as two separate units. We recommend that they collaborate more closely to deal with mixed or concomitant infections.

Interestingly, the literature suggests that the best time to diagnose filariasis is during late evening hours (Hawkings 1979), but during this study W. bancrofti cases were detected during the day, suggesting that daytime diagnosis may be appropriate as well and that the periodicity of this microfilariae in Guyana may not be strictly nocturnal but rather aperiodic. Further study is necessary to characterize this aperiodic behaviour.

Data on the gender of persons infected with concomitant infections showed that males were significantly more often (P > 0.01) afflicted. Men working in the interior of Guyana, which is endemic for both malaria and filariasis, may have been occupationally exposed in gold mines, the lumber industry or other forest-related work. The fact that no malaria or concomitant infections occurred among the 0–9 age group suggests that travel into the forested interior or high risk endemic areas along the coastal margins may be the cause of infection.

Nathan and Stroom (1990) reported a higher prevalence of W. bancrofti infections among people of African origin (7.7%) than other ethnic groups in Guyana. We obtained similar results with more than 77% of the 103 W bancrofti cases occurring among persons of African origin.

It is noteworthy that the incidence of cerebral malaria among Guyanese nationals < 5% despite the high incidence of malaria in Guyana (Chadee 1998), the occurrence of chloroquine-resistant strains of P. falciparum (Chadee et al. 1985) and the presence of suitable vectors (Rambajan 1998). Cerebral malaria is most frequent among tourist and expatriate workers (Chadee et al. 1985; Chadee et al. 1996).

In Guyana, the Culex quinquefasciatus Say mosquito is the main vector of Bancroftian filariasis especially in urban coastal areas of Guyana (Giglioli 1948), while Anopheles darlingi is the primary vector of malaria in the interior of the country. In the coastal areas A. aquasalis is an important vector of both malaria and filariasis, but the incidence of malaria on the coast is relatively low (Validum 1998). These factors may well explain the low transmission of concomitant infections among coastal dwellers by this vector species.

Acknowledgements

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results
  6. Nocturnal survey
  7. Diurnal survey
  8. Discussion
  9. Acknowledgements
  10. References

We thank the dedicated staff of both the Malaria and Filariasis Clinics, Ministry of Health, Georgetown, Guyana for their support throughout this study.

References

  1. Top of page
  2. Summary
  3. Introduction
  4. Materials and methods
  5. Results
  6. Nocturnal survey
  7. Diurnal survey
  8. Discussion
  9. Acknowledgements
  10. References
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  • Petrie A & Sabin C (2000) Medical Statistics at a Glance. Blackwell Science, Oxford.
  • Rambajan I (1998) Observations on Anopheles aquasalis Curry and malaria transmission in Guyana, South America. Suriname Medical Bulletin 13, 214.
  • Rawlins SC, Lammie P, Tewari T et al. (1999) Lymphatic filariasis in the Caribbean region: the opportunity for its elimination and certification. Pan American Journal of Public Health 7, 319323.
  • Validum L (1998) Malaria returns. Anopheles darlingi, the scourge of generations, is back. Guyana Review 5, 816.