Improved molecular detection of Babesia infections in animals using a novel quantitative real-time PCR diagnostic assay targeting mitochondrial DNA

BACKGROUND

Babesiosis is a protozoal, tick transmitted disease found worldwide in humans, wildlife and domesticated animals. Commonly used approaches to diagnose babesiosis include microscopic examination of peripheral blood smears, detection of circulating antibodies and PCR. To screen and differentiate canine Babesia infections many PCR assays amplify the 18S rRNA gene. These sequences contain hypervariable regions flanked by highly conserved regions allowing for amplification of a broad-range of Babesia spp. However, differences in the 18S rRNA gene sequence of distantly related clades can make it difficult to design assays that will amplify all Babesia species while excluding the amplification of other eukaryotes. By targeting Babesia mitochondrial genome (mtDNA), we designed a novel three primer qPCR with greater sensitivity and broader screening capabilities to diagnose and differentiate Babesia spp.

METHODS

Using 13 Babesia mtDNA sequences, a region spanning two large subunit rRNA gene fragments (lsu5-lsu4) was aligned to design three primers for use in a qPCR assay (LSU qPCR) capable of amplifying a wide range of Babesia spp. Plasmid clones were generated and used as standards to determine efficiency, linear dynamic range and analytical sensitivity. Animals naturally infected with vector-borne pathogens were tested retrospectively and prospectively to determine relative clinical sensitivity and specificity by comparing the LSU qPCR to an established 18S rDNA qPCR.

RESULTS

The LSU qPCR efficiencies ranged between 92 and 100% with the limit of detection at five copies/reaction. The assay did not amplify mammalian host or other vector-borne pathogen gDNA except Cytauxzoon felis (a feline protozoal pathogen). The LSU qPCR assay amplified 12 different Babesia. sp. and C. felis from 31/31 (100%) archived samples, whereas the 18S qPCR amplified only 26/31 (83.9%). By prospective analysis, 19/394 diagnostic accessions (4.8%) were LSU qPCR positive, compared to 11/394 (2.8%) 18S rDNA qPCR positive.

CONCLUSIONS

We have developed a more sensitive qPCR assay with a more expansive range of Babesia spp. detection by targeting a highly conserved region of mtDNA, when compared to an established 18S qPCR.

Rickettsia typhi infection in a clinically-ill dog from Houston, Texas

In 2020, Rickettsia typhi was diagnosed in a dog from Houston, Texas, USA based upon R. typhi IFA seroreactivity in both acute and convalescent sera, and PCR with DNA sequencing of 4 different gene regions, all of which were 100% identical to R. typhi. The dog was clinically ill with intermittent fever, lethargy, inappetence, and lymphadenopathy. Clinicopathological abnormalities included a mild nonregenerative anemia, neutrophilia, lymphopenia, thrombocytopenia, hypoalbuminemia, and elevated ALP. The dog rapidly recovered with doxycycline administration.

Fluoride concentrations in bottled water

Bottled water use and lack of adequate labeling have given rise to questions regarding fluoride intake. This study examined fluoride concentration of commercially available bottled water products, determined if significant differences existed among the products, and explored packaging date as a variable on the concentration of fluoride. The values were compared to the ADA guideline for optimally fluoridated water and the American Academy of Pediatric Dentistry recommended schedule for fluoride supplementation. Five commercial brands were chosen for the study. Three bottles of each brand, each with different batch dates, were purchased. Following calibration, six tests were conducted on each bottle using the Hach DR-100 Colorimeter System for fluoride analysis and the values were recorded. Data were analyzed using a two-tailed ANOVA and Tukey's HSD Test (p = 0.05). The results showed that significant differences in fluoride concentrations existed among the five brands. For three brands, significant differences existed between the batches. All products had fluoride concentrations that fell below the ADA accepted standards for optimally fluoridated water. Due to the significant variability in fluoride concentration between products and batches, dental providers should advise their patients that bottled water might not contain optimal levels of fluoride.