Plasmodium knowlesi is the major cause of zoonotic malaria in Southeast Asia. Rapid and accurate diagnosis enables effective clinical management. A novel malaria diagnostic tool, Gazelle (Hemex Health, USA) detects haemozoin, a by-product of haem metabolism found in all Plasmodium infections. A pilot phase refined the Gazelle haemozoin identification algorithm, with the algorithm then tested against reference PCR in a larger cohort of patients with P. knowlesi mono-infections and febrile malaria-negative controls. Limit-of-detection analysis was conducted on a subset of P. knowlesi samples serially diluted with non-infected whole blood. The pilot phase of 40 P. knowlesi samples demonstrated 92.5% test sensitivity. P. knowlesi-infected patients (n = 203) and febrile controls (n = 44) were subsequently enrolled. Sensitivity and specificity of the Gazelle against reference PCR were 94.6% (95% CI 90.5-97.3%) and 100% (95% CI 92.0-100%) respectively. Positive and negative predictive values were 100% and 98.8%, respectively. In those tested before antimalarial treatment (n = 143), test sensitivity was 96.5% (95% CI 92.0-98.9%). Sensitivity for samples with ≤ 200 parasites/µL (n = 26) was 84.6% (95% CI 65.1-95.6%), with the lowest parasitaemia detected at 18/µL. Limit-of-detection (n = 20) was 33 parasites/µL (95% CI 16-65%). The Gazelle device has the potential for rapid, sensitive detection of P. knowlesi infections in endemic areas.
Tick-borne pathogens are causing severe diseases in livestock, wild animals, and humans. Wild animals play a crucial role in tick-borne pathogens' transmission life cycle by serving as reservoir hosts or intermediate hosts, posing a continuous risk for domestic animals and humans. The presence of tick-borne pathogens is often ignored in wild animals kept in zoos, which is a public health concern. In the present study, we investigated these pathogens in tick-infested captive wild animals at the Lohi Bher zoo, Pakistan. Blood samples were collected from 22 animals, which include urials (4) (Ovis aries vignei), blackbucks (3) (Antilope cervicapra), fallow deer (1) (Dama dama), hog deer (6) (Axis porcinus), chinkaras (4) (Gazella bennettii), white tiger (2) (Panthera tigris tigris), a giraffe (Giraffa camelopardalis), and African lions (2) (Panthera leo). The samples were screened for Piroplasm and Anaplasma spp. by polymerase chain reaction targeting different gene loci. We detected three Theileria spp. and one Anaplasma sp. from the investigated captive wild animals. The Theileria sp. dama gazelle was detected from chinkara, Theileria sp. NG-2012b from chinkara and giraffe and T. parva from African lion, and Anaplasma bovis was identified in a giraffe. Moreover, Theileria sp. and Anaplasma sp. coinfection was detected in one giraffe. Overall, this study shows that Theileria spp. and Anaplasma spp. are circulating in captive wild animals, which can play an important role in their spread. Further studies are required to monitor tick-borne pathogens in zoo animals and their potential to spread from exotic wild captive animals to local wild and domestic.