This is a really interesting paper from Switzerland. I tried to upload it but it seems to be too big for PR. It is good that they used 'up to date' molecular methods (Next Generation Sequencing, and Quantitative PCR) to study the bacteria. The authors explain that "Borrelia burgdorferi sensu lato is a complex of spirochete bacteria that causes Lyme borreliosis (LB), t.. 'In Europe, the two most common etiological agents of LB are Borrelia afzelii and Borrelia garinii. These two Borrelia genospecies are sympatric in distribution but are adapted to different classes of vertebrate reservoir hosts: rodents and birds, respectively.." So - if one is positive for B. afzelii (as in my case) - the tick probably came from a rodent? (in Europe). I wonder which rodents in Australia carry this? Or maybe marsupials? And - if one is positive for B. garinii, the tick probably came from a bird. Also - this might explain to the many doctors who have not been trained in microbiology that the 'B.burgdorferi sensu lato' group includes other species of Borrelia, apart from B. burgdorferi. The paper: Durand J, Herrmann C, Genné D, Sarr A, Gern L, Voordouw MJ. 2017. Multistrain infections with Lyme borreliosis pathogens in the tick vector. Appl Environ Microbiol 83: e02552-16. https://doi.org/10.1128/ AEM.02552-16. Title: Multistrain Infections with Lyme Borreliosis Pathogens in the Tick Vector ABSTRACT Mixed or multiple-strain infections are common in vector-borne diseases and have important implications for the epidemiology of these pathogens. Previous studies have mainly focused on interactions between pathogen strains in the vertebrate host, but little is known about what happens in the arthropod vector. Borrelia afzelii and Borrelia garinii are two species of spirochete bacteria that cause Lyme borreliosis in Europe and that share a tick vector, Ixodes ricinus. Each of these two tick-borne pathogens consists of multiple strains that are often differentiated using the highly polymorphic ospC gene. For each Borrelia species, we studied the frequencies and abundances of the ospC strains in a wild population of I. ricinus ticks that had been sampled from the same field site over a period of 3 years. We used quantitative PCR (qPCR) and 454 sequencing to estimate the spirochete load and the strain diversity within each tick. For B. afzelii, there was a negative relationship between the two most common ospC strains, suggesting the presence of competitive interactions in the vertebrate host and possibly the tick vector. The flat relationship between total spirochete abundance and strain richness in the nymphal tick indicates that the mean abundance per strain decreases as the number of strains in the tick increases. Strains with the highest spirochete load in the nymphal tick were the most common strains in the tick population. The spirochete abundance in the nymphal tick appears to be an important life history trait that explains why some strains are more common than others in nature. IMPORTANCE Lyme borreliosis is the most common vector-borne disease in the Northern Hemisphere and is caused by spirochete bacteria that belong to the Borrelia burgdorferi sensu lato species complex. These tick-borne pathogens are transmitted among vertebrate hosts by hard ticks of the genus Ixodes. Each Borrelia species can be further subdivided into genetically distinct strains. Multiple-strain infections are common in both the vertebrate host and the tick vector and can result in competitive interactions. To date, few studies on multiple-strain vector-borne pathogens have investigated patterns of co-occurrence and abundance in the arthropod vector. We demonstrate that the abundance of a given strain in the tick vector is negatively affected by the presence of coinfecting strains. In addition, our study suggests that the spirochete abundance in the tick is an important life history trait that can explain why some strains are more common in nature than others.