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CDC Experience with Laboratory Tests Used to Investigate Incidents of Transfusion-Transmitted Malaria

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CDC Experience with Laboratory Tests Used to Investigate Incidents of Transfusion-Transmitted Malaria

FDA Workshop on Testing for Malarial Infections in Blood Donors
July 12, 2006

Marianna Wilson
Division of Parasitic Diseases
Centers for Disease Control and Prevention
Atlanta, GA


DIAGNOSTIC TOOLS AVAILABLE AT CDC

 

  • Blood film examination
  • Antibody detection - IFA
  • DNA detection - PCR

 


MALARIA IFA TEST

Antigen: washed cell thick smears of RBCs infected with one species
- P. falciparum
- P. malariae
- P. ovale
- P. vivax


MALARIA IFA TEST

 

  • Sensitivity 89/92 = 98%
    • Based on Pv and Pf infections
  • Specificity 1/184 = 99.5%
    • Babesia may cross-react

 


MALARIA IFA TEST
Human Experimental Infections

 

  • Parasitemia preceeds antibody
    • P. falciparum 4-6 days
    • P. vivax 2-6 days
    • P. malariae 4-6 days
  • If parasitemia is suppressed, may still develop detectable antibody

 


MALARIA IFA TEST
Antibody Persistence Post-Rx

 


Typical Malaria IFA Results

Slide DiagnosisP. falcipIFA
P. malariae
P. ovaleP. vivax
P. falciparum1:163841:40961:10241:64
P. falciparum1:1024NegNegNeg
P. ovaleNegNeg1:256Neg
P. vivaxNegNeg1:641:1024
P. malariae1:10241:10241:641:64

CDC PCR FOR MALARIA

Two-step nested PCR

 

  • Genus-specific primers followed by
  • Species-specific primers (Snounou et al, 1993)

 


CDC PCR FOR MALARIA

Sensitivity & Specificity
100%+
based on smear results


ALGORITHM FOR LABORATORY TESTING OF SUSPECT DONORS

 

  • Screen with serology
  • PCR on IFA positives
  • Blood film examination on IFA positives

 


TRANSFUSION TRANSMITTED MALARIA, 1963-1998
How 65 implicated donors were identified

 


TRANSFUSION TRANSMITTED MALARIA, 1963-1998

In implicated donors, where information was available:

  • 98% had positive serology
  • 33% had positive blood smear

 


Laboratory investigation of blood donors, 1996-2005

YearSpeciesDonorsIFA +PCR +
1996Falcip711
1998Falcip411
2002Malariae1010
2003Falcip210
2005Falcip1501/1000

Laboratory investigation of blood donors, 1996-2005

YearTx dateSpec dateSlide resultPCR result
199611/12/963/1997PosPos
19981/15/98?1/15/98NegPos
20025/1/027/11/02NegNeg
20033/1/034/03NegNeg
20056/30/058/29/05NegNeg

Detection of Parasites/Parasite Products

 


Detection of Parasites/Parasite Products

 


Selected References

IFA

  • Collins et al, Amer J Trop Med Hyg 1964;13:256
  • Collins et al, Amer J Trop Med Hyg 1964;13:777
  • Sulzer et al, Amer J Trop Med Hyg 1969;18:199
  •  
  • Wilson et al, Amer J Trop Med Hyg 1970;19:401 Gleason et al, Amer J Trop Med Hyg 1971;20:10

 

PCR

  • Snounou et al, Mol Biochem Parasitol 1993;61:315
  • Johnston et al, J Clin Microbiol 2006;44:1087