• View in gallery

    Percentage infection of 845 lots of Anopheles quadrimaculatus mosquitoes fed on patients during primary infections with the St. Elizabeth strain of Plasmodium vivax.

  • View in gallery

    Percentage infection of 986 lots of Anopheles quadrimaculatus mosquitoes fed on patients infected with the St. Elizabeth strain of Plasmodium vivax as related to density of microgametocytes.

  • View in gallery

    Distribution of percentage of Anopheles quadrimaculatus mosquitoes infected by feeding on patients infected with the St. Elizabeth strain of Plasmodium vivax as related to presence of fever (101–104.8°F and ≥ 105°F) and asexual parasite count/μL.

  • View in gallery

    Percentage infection of 76 lots of Anopheles quadrimaculatus mosquitoes fed on patients during secondary infections with the St. Elizabeth strain of Plasmodium vivax.

  • 1

    Collins WE, Jeffery GM, 1999. A retrospective examination of sporozoite- and trophozoite-induced infections with Plasmodium falciparum: development of parasitologic and clinical immunity during primary infection. Am J Trop Med Hyg 61 (Suppl):4–19.

    • Search Google Scholar
    • Export Citation
  • 2

    Collins WE, Jeffery GM, 1999. A retrospective examination of secondary sporozoite- and trophozoite-induced infections with Plasmodium falciparum: development of parasitologic and clinical immunity following secondary infection. Am J Trop Med Hyg 61 (Suppl):20–35.

    • Search Google Scholar
    • Export Citation
  • 3

    Collins WE, Jeffery GM, 1999. A retrospective examination of secondary sporozoite- and trophozoite-induced infections with Plasmodium falciparum in patients previously infected with heterologous species of Plasmodium: effect on development of parasitologic and clinical immunity. Am J Trop Med Hyg 61 (Suppl):36–43.

    • Search Google Scholar
    • Export Citation
  • 4

    Collins WE, Jeffery GM, 1999. A retrospective examination of patterns of recrudescence in patients infected with Plasmodium falciparum.Am J Trop Med Hyg 61 (Suppl):44–48.

    • Search Google Scholar
    • Export Citation
  • 5

    Diebner HH, Eichner M, Molineaux L, Collins WE, Jeffery GM, Dietz K, 2000. Modelling the transition to gametocytes from asexual blood stages of Plasmodium falciparum.J Theorl Biol 202 :113–127.

    • Search Google Scholar
    • Export Citation
  • 6

    Molineaux L, Diebner HH, Eichner M, Collins WE, Jeffery GM, Dietz K, 2001. Plasmodium falciparum parasitemia described by a new mathematical model. Parasitology 122 :379–391.

    • Search Google Scholar
    • Export Citation
  • 7

    Makenzie FE, Collins WE, Jeffery GM, 2001. Plasmodium malariae blood stage dynamics. J Parasitol 87 :626–638.

  • 8

    Collins WE, Jeffery GM, 2002. A retrospective examination of sporozoite- and trophozoite-induced infections with Plasmodium ovale: development of parasitologic and clinical immunity during primary infection. Am J Trop Med Hyg 66 :492–502.

    • Search Google Scholar
    • Export Citation
  • 9

    Simpson JA, Aarons L, Collins WE, Jeffery GM, White NJ, 2002. Population dynamics of untreated Plasmodium falciparum malaria within the adult host during the expansion phase of the infection. Parasitology 124 :247–263.

    • Search Google Scholar
    • Export Citation
  • 10

    Eichner M, Diebner HH, Molineaux L, Collins WE, Jeffery GM, Dietz K, 2001. Genesis, sequestration, and survival of Plasmodium falciparum gametocytes. Parameter estimates from fitting a model to malariatherapy data. Trans R Soc Trop Med Hyg 95 :497–501.

    • Search Google Scholar
    • Export Citation
  • 11

    Molineaux L, Trauble M, Collins WE, Jeffery GM, Dietz K, 2002. Malaria therapy reinoculation data suggest individual variation in an inate immune response and independent acquisition of antiparasitic and antitoxic immunities. Trans R Soc Trop Med Hyg 96 :205–209.

    • Search Google Scholar
    • Export Citation
  • 12

    McKenzie E, Barnwell JW, Jeffery GM, Collins WE, 2002. Plasmodium vivax blood-stage dynamics. J Parasitol 88 :521–535.

  • 13

    McKenzie FE, Jeffery GM, Collins WE, 2002. Plasmodium malariae infection boosts Plasmodium falciparum gametocyte production. Am J Trop Med Hyg 67 :411–414.

    • Search Google Scholar
    • Export Citation
  • 14

    Collins WE, Jeffery GM, Roberts JM, 2003. A retrospective examination of anemia during infection of humans with Plasmodium vivax.Am J Trop Med Hyg 68 :410–412.

    • Search Google Scholar
    • Export Citation
  • 15

    Collins WE, Jeffery GM, 2003. A retrospective examination of mosquito infection on humans infected with Plasmodium falciparum.Am J Trop Med Hyg 68 :366–371.

    • Search Google Scholar
    • Export Citation
  • 16

    Collins WE, Jeffery GM, Roberts JM, 2004. A retrospective examination of reinfection of humans with Plasmodium vivax.Am J Trop Med Hyg 70 :642–644.

    • Search Google Scholar
    • Export Citation
  • 17

    Earle WC, Perez M, 1932. Enumeration of parasites in the blood of malarial patients. J Lab Clin Med 17 :1124–1130.

 

 

 

 

A RETROSPECTIVE EXAMINATION OF THE EFFECT OF FEVER AND MICROGAMETOCYTE COUNT ON MOSQUITO INFECTION ON HUMANS INFECTED WITH PLASMODIUM VIVAX

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  • 1 Division of Parasitic Diseases, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia

A retrospective examination was made of archival data collected between 1940 and 1963 on the infection of mosquitoes with the St. Elizabeth strain of Plasmodium vivax. Patients were undergoing malariatherapy for the treatment of neurosyphilis. A total of 845 lots of Anopheles quadrimaculatus mosquitoes were fed during primary infections and 76 during secondary infections. Average percentage infection during the primary infection was 56.55% versus 49.83% during the secondary infection. There appeared to be no relationship between microgametocye density, asexual parasite count, and percentage infection. However, very high fevers appear to have a significant effect on infection rates. Persons with fever ≥ 105°F showed the lowest rates of infectivity regardless of parasitemia; persons with moderate (101–104.8°F) fever produced somewhat higher rates, and persons with no fever had the highest levels of infection at all parasitemia levels greater than 1,500/μL

INTRODUCTION

Analyses are being made of archival data from patients infected with malaria between 1940 and 1963 for the treatment of neurosyphilis to better understand the development of immunity to infection and the relationships between the parasite and its human host and its vectors.1–16 Previously, blood-stage dynamics of P. vivax12,14 was reported, and mosquito relationships for P. ovale8 and P. falciparum15 were presented. Sporozoite-induced infections were often used because of the potential problems associated with blood passage. Whenever a new patient needed to be treated, mosquitoes would be fed on an infected patient, if available.

Reported here are the results of a retrospective examination of archival data from mosquito feedings on 166 induced infections with P. vivax for the treatment of paresis and other mental disorders associated with tertiary syphilis. The goal was to further document 1) the relationship between microgametocyte count and mosquito infection, and 2) the effect, if any, of asexual parasite count or fever on percentage of mosquitoes infected.

MATERIALS AND METHODS

Patient management.

Consent for whatever treatments the hospital staff determined necessary for the patients was granted by the families of the patients or the courts when patients were admitted to the hospital. The decision to infect a neurosyphilitic patient with a specific malaria was made as part of standard patient care by the medical staff of the South Carolina State Hospital. Patient care and evaluation of clinical endpoints (e.g., fever) were the responsibility of the medical staff. As previously reported,2 during infection, the temperature, pulse, and respiration were checked every four hours and hourly during paroxysms (fevers) by hospital personnel. During paroxysms, patients were treated symptomatically. Infections were terminated at the direction of the attending physician. The U.S. Public Health Service personnel provided the parasites for inoculation, monitored the daily parasite counts to determine the course of infection, provided mosquitoes to be fed on the patients, and performed mosquito dissections and examinations. All patients undergoing malariatherapy lived in screened wards of the hospital to prevent possible infection of local anophelines.

Treatment.

Infections were terminated by treatment with various antimalarial drugs. In addition, various drugs, such as primaquine, pyrimethamine, quinine, and chlorguanide are all capable of at least temporarily preventing mosquito infection, without permanently eliminating the infection in the human host. Patients receiving treatments that may have had an effect on mosquito infection were excluded from the current analysis.

Strain of Plasmodium vivax.

The 166 patients were infected with the St. Elizabeth strain that was obtained from St. Elizabeth Hospital in Washington, D.C. in the 1930s. The exact parasite origin is unknown.

Parasitemia.

Patients were infected by the intravenous inoculation of parasitized erythrocytes or via sporozoite inoculation. Thick and thin peripheral blood films were made daily by the method of Earle and Perez,17 stained with Giemsa, and examined microscopically for the presence of parasites. The threshold of detection was approximately 10 parasites/μL. Asexual and sexual parasites were recorded per microliter of blood. Infections often persisted for many weeks. However, most of the patients were fed upon during the initial 40 days of patent parasitemia.

Mosquitoes.

Anopheles quadrimaculatus mosquitoes were laboratory reared, caged, and allowed to feed to repletion directly on the patients. Mosquitoes that fed were subsequently dissected and the number of oocysts present on the midguts counted and recorded.

Data analysis.

Poisson regression was used to investigate the effect of fever and parasitemia on malaria infection rates. Orthogonal contrasts were used to compare infection rates by fever status at varying levels of parasitemia. Pearson correlation was used to quantify the association between infectivity and microgametocyte count. SAS version 8.0, (SAS Institute, Cary, NC) was used to analyze data. Statistical significance was set at P < 0.05.

RESULTS

During primary infection with the St. Elizabeth strain of P. vivax, 845 lots of An. quadrimaculatus mosquitoes were fed and examined (Figure 1). Of these, the average percentage infection of mosquitoes per lot was 56.6%, with greater than 50% infection rates between days 17 and 38. Thus, there was a high probability of infection when mosquitoes were fed anytime during this period. An examination was made of the possible effect of microgametocyte count on percentage infection. Counts were recorded for 986 of the days on which mosquitoes were fed. Counts ranged from > 1 to > 500/μL (Figure 2). In spite of the high percentage infection, there were still many occasions where lots were lightly infected or not at all; yet, there was a low moderate positive trend for increased percentage infection with increased microgametocyte count (r = 0.22, P < 0.001).

An examination was made of the possible relationship between fever, the asexual parasite count, and percentage infection (Figure 3). Parasitemia was categorized at four levels, namely, < 2,500, 2,501–5,000, 5,001–10,000, and > 10,000/μL. Fever status was defined as having no fever (<101°F), 101–104.8°F, and ≥ 105°F. Infection rates for persons with very high (≥ 105°F) fevers remained low and relatively constant across the four levels of parasitemia with 42.1%, 41.9%, 43.7%, and 43.9% infection, respectively. Persons with no fever had significantly (P < 0.001) higher rates of infection than did persons with fevers ≥ 105°F at each level of parasitemia (except at < 2,500 parasites/μL) with 44.6%, 64.1%, 68.3%, and 67.6% infection, respectively. Persons with more moderate fevers (101–104.8°F) had significantly (P < 0.001) higher rates of infection at all levels of parasitemia with 51.3%, 53.6%, 61.0%, and 62.0% infection, respectively, than did persons with very high fever. Between days 9 and 16 (Figure 1), the lots of mosquitoes fed had lower average percentage infection; this coincided with the days when fever was most prevalent.

A total of 76 lots of An. quadrimaculatus mosquitoes were fed on patients during their secondary reinfections with P. vivax following previous P. vivax infection (Figure 4). Of these, the average percentage infection was 49.8% versus the 56.6% obtained during the primary infections.

DISCUSSION

An examination of the archived data showed that mosquitoes were not fed in a systematic pattern, but rather on an ad hoc basis. When infected mosquitoes were needed to transmit the infection to another patient for malariatherapy, mosquitoes were fed for one or two days with little or no rationale for expected infection. Apparently, experience had indicated that P. vivax readily infected mosquitoes and that infection could apparently be expected by feeding on any day that asexual parasites were present. An examination of the results of these feedings indicated that the success obtained was remarkable high.

Anopheles quadrimaculatus were indeed readily infected by feeding on patients infected with the St. Elizabeth strain of P. vivax. Infection did not appear to be related to the density of microgametocytes nor to the course of the parasitemia. Highest percentage mosquito infection (≥ 50%) occurred following the first two weeks of patent parasitemia and continued for the following four weeks. This long window of relatively high-density mosquito infection allowed for the continued cyclical transmission from patient to patient.

A more detailed examination of the data showed that days when mosquitoes were not infected or were of low density were more associated with days of fever, regardless of asexual parasite count or microgametocyte count. Mosquito lots fed during days of fever were more likely to have lower percentages of mosquito infection. The reasons for this are unclear, but suggest that high temperature may somehow interfere with the sexual process. The highest percentages of mosquito infection were obtained by feeding on high microgametocytemic, non-fever days during the third to sixth week of patent parasitemia.

Figure 1.
Figure 1.

Percentage infection of 845 lots of Anopheles quadrimaculatus mosquitoes fed on patients during primary infections with the St. Elizabeth strain of Plasmodium vivax.

Citation: The American Journal of Tropical Medicine and Hygiene Am J Trop Med Hyg 70, 6; 10.4269/ajtmh.2004.70.638

Figure 2.
Figure 2.

Percentage infection of 986 lots of Anopheles quadrimaculatus mosquitoes fed on patients infected with the St. Elizabeth strain of Plasmodium vivax as related to density of microgametocytes.

Citation: The American Journal of Tropical Medicine and Hygiene Am J Trop Med Hyg 70, 6; 10.4269/ajtmh.2004.70.638

Figure 3.
Figure 3.

Distribution of percentage of Anopheles quadrimaculatus mosquitoes infected by feeding on patients infected with the St. Elizabeth strain of Plasmodium vivax as related to presence of fever (101–104.8°F and ≥ 105°F) and asexual parasite count/μL.

Citation: The American Journal of Tropical Medicine and Hygiene Am J Trop Med Hyg 70, 6; 10.4269/ajtmh.2004.70.638

Figure 4.
Figure 4.

Percentage infection of 76 lots of Anopheles quadrimaculatus mosquitoes fed on patients during secondary infections with the St. Elizabeth strain of Plasmodium vivax.

Citation: The American Journal of Tropical Medicine and Hygiene Am J Trop Med Hyg 70, 6; 10.4269/ajtmh.2004.70.638

Authors’ addresses: William E. Collins, Division of Parasitic Diseases, Centers for Disease Control and Prevention, Mailstop F-36, 4770 Buford Highway, Atlanta, GA 30341, E-mail: wec1@cdc.gov. Geoffrey M. Jeffery (Public Health Service, retired), 1093 Blackshear Drive, Decatur, GA 30033. Jacquelin M. Roberts, Division of Parasitic Diseases, Centers for Disease Control and Prevention, Mailstop F-22, 4770 Buford Highway, Atlanta, GA 30341, E-mail: jmr1@cdc.gov.

REFERENCES

  • 1

    Collins WE, Jeffery GM, 1999. A retrospective examination of sporozoite- and trophozoite-induced infections with Plasmodium falciparum: development of parasitologic and clinical immunity during primary infection. Am J Trop Med Hyg 61 (Suppl):4–19.

    • Search Google Scholar
    • Export Citation
  • 2

    Collins WE, Jeffery GM, 1999. A retrospective examination of secondary sporozoite- and trophozoite-induced infections with Plasmodium falciparum: development of parasitologic and clinical immunity following secondary infection. Am J Trop Med Hyg 61 (Suppl):20–35.

    • Search Google Scholar
    • Export Citation
  • 3

    Collins WE, Jeffery GM, 1999. A retrospective examination of secondary sporozoite- and trophozoite-induced infections with Plasmodium falciparum in patients previously infected with heterologous species of Plasmodium: effect on development of parasitologic and clinical immunity. Am J Trop Med Hyg 61 (Suppl):36–43.

    • Search Google Scholar
    • Export Citation
  • 4

    Collins WE, Jeffery GM, 1999. A retrospective examination of patterns of recrudescence in patients infected with Plasmodium falciparum.Am J Trop Med Hyg 61 (Suppl):44–48.

    • Search Google Scholar
    • Export Citation
  • 5

    Diebner HH, Eichner M, Molineaux L, Collins WE, Jeffery GM, Dietz K, 2000. Modelling the transition to gametocytes from asexual blood stages of Plasmodium falciparum.J Theorl Biol 202 :113–127.

    • Search Google Scholar
    • Export Citation
  • 6

    Molineaux L, Diebner HH, Eichner M, Collins WE, Jeffery GM, Dietz K, 2001. Plasmodium falciparum parasitemia described by a new mathematical model. Parasitology 122 :379–391.

    • Search Google Scholar
    • Export Citation
  • 7

    Makenzie FE, Collins WE, Jeffery GM, 2001. Plasmodium malariae blood stage dynamics. J Parasitol 87 :626–638.

  • 8

    Collins WE, Jeffery GM, 2002. A retrospective examination of sporozoite- and trophozoite-induced infections with Plasmodium ovale: development of parasitologic and clinical immunity during primary infection. Am J Trop Med Hyg 66 :492–502.

    • Search Google Scholar
    • Export Citation
  • 9

    Simpson JA, Aarons L, Collins WE, Jeffery GM, White NJ, 2002. Population dynamics of untreated Plasmodium falciparum malaria within the adult host during the expansion phase of the infection. Parasitology 124 :247–263.

    • Search Google Scholar
    • Export Citation
  • 10

    Eichner M, Diebner HH, Molineaux L, Collins WE, Jeffery GM, Dietz K, 2001. Genesis, sequestration, and survival of Plasmodium falciparum gametocytes. Parameter estimates from fitting a model to malariatherapy data. Trans R Soc Trop Med Hyg 95 :497–501.

    • Search Google Scholar
    • Export Citation
  • 11

    Molineaux L, Trauble M, Collins WE, Jeffery GM, Dietz K, 2002. Malaria therapy reinoculation data suggest individual variation in an inate immune response and independent acquisition of antiparasitic and antitoxic immunities. Trans R Soc Trop Med Hyg 96 :205–209.

    • Search Google Scholar
    • Export Citation
  • 12

    McKenzie E, Barnwell JW, Jeffery GM, Collins WE, 2002. Plasmodium vivax blood-stage dynamics. J Parasitol 88 :521–535.

  • 13

    McKenzie FE, Jeffery GM, Collins WE, 2002. Plasmodium malariae infection boosts Plasmodium falciparum gametocyte production. Am J Trop Med Hyg 67 :411–414.

    • Search Google Scholar
    • Export Citation
  • 14

    Collins WE, Jeffery GM, Roberts JM, 2003. A retrospective examination of anemia during infection of humans with Plasmodium vivax.Am J Trop Med Hyg 68 :410–412.

    • Search Google Scholar
    • Export Citation
  • 15

    Collins WE, Jeffery GM, 2003. A retrospective examination of mosquito infection on humans infected with Plasmodium falciparum.Am J Trop Med Hyg 68 :366–371.

    • Search Google Scholar
    • Export Citation
  • 16

    Collins WE, Jeffery GM, Roberts JM, 2004. A retrospective examination of reinfection of humans with Plasmodium vivax.Am J Trop Med Hyg 70 :642–644.

    • Search Google Scholar
    • Export Citation
  • 17

    Earle WC, Perez M, 1932. Enumeration of parasites in the blood of malarial patients. J Lab Clin Med 17 :1124–1130.

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