Molecular epidemiology, symptomatic analysis of anaplasmosis and associated study of milk reduction in cattle from district Nowshera, KP, Pakistan

Anaplasma is an obligate intracellular bacterium that cause anaplasmosis. The two species of Anaplasma namely Anaplasma marginale and Anaplasma centrale affects cattle, buffaloes, sheep, goats and wild ruminants. This rickettsial microorganism, which is transmitted by ticks, is causing massive economic losses due to weight loss, decreased milk supply, severe anemia and high mortality. The research study was conducted between May 2023 to April 2024 to determine the prevalence, symptomatic analysis of anaplasmosis and associated study of milk reduction in cattle from district Nowshera, KP, Pakistan. Total 635 blood specimens were obtained from different cattle herds coming from 17 farms. Such blood specimens underwent microscopic examination by using Giemsa-stained blood smears and troughs molecular analysis by PCR targeting the msp1b gene (265 bp fragment) in order to detect A. marginale. All relevant statistical analyses, including Chi-square tests, were carried out with SPSS to test for significance (p < 0.05). Combining microscopy and PCR, the overall prevalence of A. marginale was determined to be 13.3% (n = 85) and 12.7% (n = 81) respectively. Age-wise prevalence revealed that younger cattle (< 5 years) had significantly higher infection rates 62.3% (n = 53) as compared to older cattle (> 5 years) 37.6% (n = 32), with a p-value of 0.037. Of the PCR-positive cases, 64.1% (n = 52) were from younger cattle and 35.8% (n = 29) were from older cattle. A potential cause for the relatively low PCR positivity in comparison to microscopic identification is that certain false-positive microscopic identifications based on Heinz bodies or other blood artifacts as Anaplasma species may be involved. Naturally, PCR would only target the genetic material of the actual disease. Microscopy showed that prevalence peaked in the month of July at 24.7%, while PCR recorded peak prevalence in June at 33.3%. There were no confirmed cases in January and February, confirming that the differences in seasonal prevalence were statistically significant (p < 0.05). In terms of production loss, one-year-old Holstein cows experienced a 47% reduction in milk yield post-infection (from 17 L to 9 L), while cows 2 to 7 years-old exhibited reductions ranging from 50 to 75%, all statistically significant. It was concluded that anaplasmosis was widely distributed in district Nowshera and it is high economic losses on dairy farm. Further research is needed to develop control measures and to improve understanding of the disease transmission.