avian & livestock assay data sheet

Malaria (Plasmodium species)

Test code: X0014 - Ultrasensitive qualitative screen for Plasmodium species by real time PCR. This assay detects but does not differentiate most malaria-causing Plasmodium species, including P. falciparum, P. malariae, P. vivax, P. ovale, P. knowlesi, P. fieldi, P. hylobati, P. juxtanucleare, P. yoelii, P. brasilianum, P. cynomolgi, P. inui, P. schwetzi, P. reichenowi, P. eyles, P.jefferyi, P. youngi, P. pitheci, P. silvaticum, P. coatneyi, P. fragile, P. simiovale, P. gonderi, P. brasilianum, P. simium, P. cathemerium and P. gallinaceum.

Malaria is caused by protozoan parasites of the genus Plasmodium. The parasites are transmitted by infected Anopheles mosquitos. As the infected female mosquito takes a blood meal, it injects the parasite, which travels in the bloodstream to the liver. Inside the liver, the organism undergoes several developmental changes leading to the release of a large number of merozoites. These merozoites invade the red blood cells. The asexual stages often seen in blood films are young trophozoites (also known as “ring forms”), mature trophozoites, and the dividing schizonts that yield the merozoites for a new generation.

Many species of Plasmodium infect birds (Jones & Shellam, 1999). Some are host species specific; others infect a range of avian species.  Birds infected with Plasmodium are often subclinical, making identification of carriers extremely difficult. The genetic sequences of many species of Plasmodium which infect birds are not yet fully characterized. However, assay X0014 is designed to detect a broad range of Plasmodium species based on current sequence information, but to avoid cross-reaction with non-Plasmodium species which could potentially be found in avian blood.

Traditionally, malaria screening and diagnosis relied on microscopic examination of blood smears. This method is fast and cheap but has a very low sensitivity. Successful detection in blood smears also depends on collecting the specimen at the peak of the parasitemia. Antibody detection can be used to diagnose the disease but paired serum samples several weeks apart are required in order to identify actively infected animals, making rapid diagnosis impossible. Furthermore, most serology testing currently available targets the Plasmodium species that infect humans, such as P. malariae, P. falciparum, P. vivax and P. ovale. Reagents used for these human serology tests are not appropriate for screening birds. Molecular detection by PCR is a rapid, specific and sensitive method for accurately diagnosing and identifying carriers.

Utilities:

• Confirm the disease causing agent
• Shorten the time required to confirm a clinical diagnosis of Plasmodium infection
• Ensure that bird populations are free of Plasmodium
• Early prevention of spread of malaria among a flock
• Minimize human exposure to Plasmodium
• Safety monitoring of biological products that derive from birds

References:
Jones, H.I. & Shellam, G.R. 1999. Blood parasites in penguins, and their potential impact on conservation. Marine Ornithology 27: 181–184.

Specimen requirements: 0.2 ml whole blood in EDTA (purple top) or ACD (yellow top) tube.

For specimen types other than those listed here, please call to confirm specimen acceptability and shipping instructions.

For all specimen types, if there will be a delay in shipping, or during very warm weather, refrigerate specimens until shipped and ship with a cold pack unless more stringent shipping requirements are specified. Frozen specimens should be shipped so as to remain frozen in transit. See shipping instructions for more information.

Turnaround time: 2 business days

Methodology: Qualitative PCR

Normal range: Nondetected