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This article is about testing sheep for low level chronic babesia infections or as they phrased it - subclinical babesia.
It shows how inaccurate the current commercially available PCR tests are. I recently read in the book Lyme Disease Update: Science, Policy and Law that doing 5 PCR tests could help to detect a low level babesia infection - yes you read that right - you need to repeat the test 5 times which of course insurance would never pay for. You would be lucky if they would pay one time.
In the journal article the standard PCR test was positive for 5 out of 300 samples from sheep and zero of 39 ticks. Using the special PCR techinique the results were 38 out of 300 sheep tested positive and 7 out of 39 ticks. Quite a difference.
Babesia ovis is a tick-transmitted protozoa parasite that infects small ruminants causing fever, anaemia, hemoglobinuria, anorexia and, in acute cases, death.
Common in tropical and sub-tropical areas, the presence of this parasite in sheep herds has an economic impact on industry and therefore sensitive methods for the diagnosis and disease eradication are required.
To achieve this goal, a semi-nested PCR for B. ovis specific identification was developed and consequent reaction conditions and enzymes were optimized and tested with field samples.
300 blood samples from small ruminants and 39 ticks from Rhipicephalus genus were collected from different regions of Portugal. Afterwards, DNA extraction was performed and conventional and semi-nested PCR were accomplished for all samples. The results obtained from both methodologies were compared and the sensitivity was evaluated.
Employing the semi-nested PCR it was possible to identify a higher number of positive cases among the evaluated samples than using the conventional PCR, namely 38/300 blood samples and 7/39 ticks. However, fragment amplification was only observed in 5 out of 300 blood samples and in none of the 39 ticks when a conventional PCR was employed.
The validation of the results was achieved by sequencing the DNA fragments corresponding to the hypervariable v4 region of the 18S ribosomal RNA gene and performing an alignment with sequences already published on GenBank®.
The ticks collected in this study belong to the Rhipicephalus genus, although other species could be involved as a vector in the Babesia spread. The diagnostic assay here described is presently the most effective and sensitive method for detection of B. ovis in field blood samples and ticks, enabling the detection up to 1 parasite into 109 erythrocytes.
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For some reason when the abstract was copied the 10 to the ninth power got converted to 109.
Ok - a quick check on google says 10 to the ninth power equals 1,000,000,000. Yes, you read that right the testing technique could detect 1 infected red blood cell per one billion red blood cells.
Really curious as to the least number of infected cells a person would have to have to test positive on this new test.
Wikipedia says the body produces 2.4 million new red blood cells per second. Mind boggling.
I remember the Dr B explaining to hubby that red blood cells have to fold up to squeeze thru the capillaries. But I never knew just how large they were. Supposedly erythrocytes (red blood cells) are 25 percent larger than capillaries. Babesia infected cells are stiffer and do not bend as well as normal cells plus babesia has adhesion capabilities which means it attaches to the inside walls of the capillaries just like plaque does in cardiovascular disease.
Ok - Back to the numbers. An adult has about 20 to 30 trillion total red blood cells. Women have 4 to 5 million RBC per microliter (cubic millimeter of blood) and men have 5 to 6 million RBC.
Per google 20 or 30 trillion divided by 1 billion equals 20 or 30 thousand infected babesia cells for a subclinical infection in a human. Amazing.
So if my math is right the new improved test which is I am certain a research test ONLY can detect babesia if a person only has 20,000 or 30,000 babesia infected cells.
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To compare that to another of the tickborne diseases. I read somewhere that it only takes 50 Rocky Mountain Spotted Fever bacteria to infect a person.
Just another interesting statistic.
And for tularemia you only need 10 to 50 bacteria to infect a person.
Bea Seibert
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