Thomas Jäkel

To date, only one case is known where protozoan parasites of the genus Sarcocystis were found to infect cheetahs (Acinonyx jubatus); the cysts in the musculature were morphologically identified as S. felis. Here, we characterized sarcocysts by morphological and molecular methods that were observed in cheetahs who died in zoos in China. Only one type of sarcocyst was present in two of six cheetahs. By light microscopy, the sarcocyst wall was striated, 1.4–2.1 μm thick. Ultrastructurally, the wall had irregular-shaped, small villar protrusions, resembling wall type 9c, similar to those of S. arctica, S. caninum, and S. felis. The samples shared their highest molecular identity values with those of S. arctica and S. caninum: 99.9–100% and 99.8–100% (18S rRNA), 99.5% and 99.3–99.5% (28S rRNA), 95.9–97.5% and 96.3–97.3% (ITS-1), and 99.6% and 99.2–99.7% (cox1), respectively. Compared with ITS-1 of S. felis, identities ranged between 87.5% and 88.9%. Phylogenetic reconstruction revealed that the newly sequenced Sarcocystis clustered with S. arctica and S. caninum, whereas S. felis (ITS-1) and S. canis (ITS-1, 18S rRNA, cox1) were sister species. Thus, we addressed the Sarcocystis species from the cheetahs as S. arctica, which is the first record of a Sarcocystis species believed to be specific for canids as intermediate hosts to infect a feline host.

Background: The geographic distribution and host-parasite interaction networks of Sarcocystis spp. in small mammals in eastern Asia remain incompletely known. Methods: Experimental infections, morphological and molecular characterizations were used for discrimination of a new Sarcocystis species isolated from colubrid snakes and small mammals collected in Thailand, Borneo and China. Results: We identified a new species, Sarcocystis muricoelognathis sp. nov., that features a relatively wide geographic distribution and infects both commensal and forest-inhabiting intermediate hosts. Sarcocystis sporocysts collected from rat snakes (Coelognathus radiatus, C. flavolineatus) in Thailand induced development of sarcocysts in experimental SD rats showing a type 10a cyst wall ultrastructure that was identical with those found in Rattus norvegicus from China and the forest rat Maxomys whiteheadi in Borneo. Its cystozoites had equal sizes in all intermediate hosts and locations, while sporocysts and cystozoites were distinct from other Sarcocystis species. Partial 28S rRNA sequences of S. muricoelognathis from M. whiteheadi were largely identical to those from R. norvegicus in China but distinct from newly sequenced Sarcocystiszuoi. The phylogeny of the nuclear 18S rRNA gene placed S. muricoelognathis within the so-called S. zuoi complex, including Sarcocystisattenuati, S. kani, S. scandentiborneensis and S. zuoi, while the latter clustered with the new species. However, the phylogeny of the ITS1-region confirmed the distinction between S. muricoelognathis and S. zuoi. Moreover, all three gene trees suggested that an isolate previously addressed as S. zuoi from Thailand (KU341120) is conspecific with S. muricoelognathis. Partial mitochondrial cox1 sequences of S. muricoelognathis were almost identical with those from other members of the group suggesting a shared, recent ancestry. Additionally, we isolated two partial 28S rRNA Sarcocystis sequences from Low’s squirrel Sundasciurus lowii that clustered with those of S. scandentiborneensis from treeshews. Conclusions: Our results provide strong evidence of broad geographic distributions of rodent-associated Sarcocystis and host shifts between commensal and forest small mammal species, even if the known host associations remain likely only snapshots of the true associations. Graphical

BACKGROUND: Upon request of the local administration a control campaign targeting commensal rats (Rattus rattus, R. exulans) was conducted in 30 sub‐districts (villages) of the World Heritage town Luang Prabang, Northern Laos, using rat bait containing lethal quantities of the parasitic protist Sarcocystis singaporensis. The associated investigations assessed the short‐term control efficacy, willingness of residents to co‐operate (community approach), and temporal and spatial changes of the urban rat population in response to treatment.RESULTS: Biological rodent control significantly reduced rodent activity (percentage of positive tracking patches) in the town, from a mean of 25.3% (±12.8% SD) before (January–February) down to 8.0% (±4.4%) after (June) treatment. Reduction of rodent activity relative to three untreated villages was 83%. Similarly, residents observed significantly fewer rats on their properties after the campaign (mean percentage of households (HHs) per village with sightings), whereby reduction of sightings amounted to 57%. There was significant correlation between residents' observation rates and rodent activity. Among 94 rats trapped before and after treatment each, proportions of adult R. exulans and juvenile R. rattus were higher after rodent control, suggesting that a considerable part of the adult house rat population had been removed. Furthermore, a 5% post‐campaign incidence of infection suggested that few rats had survived bait uptake.CONCLUSION: S. singaporensis may be used successfully as tactical biocontrol agent for culling of rats in urban environments. We propose additional components of a long‐term rodent management strategy for the town, without which the impact of culling campaigns would be limited. © 2019 Society of Chemical Industry

We examined Sarcocystis spp. in giant snakes from the Indo-Australian Archipelago and Australia using a combination of morphological (size of sporocyst) and molecular analyses. We amplified by PCR nuclear 18S rDNA from single sporocysts in order to detect mixed infections and unequivocally assign the retrieved sequences to the corresponding parasite stage. Sarcocystis infection was generally high across the study area, with 78 (68%) of 115 examined pythons being infected by one or more Sarcocystis spp. Among 18 randomly chosen, sporocyst-positive samples (11 from Southeast Asia, 7 from Northern Australia) the only Sarcocystis species detected in Southeast Asian snakes was S. singaporensis (in reticulated pythons), which was absent from all Australian samples. We distinguished three different Sarcocystis spp. in the Australian sample set; two were excreted by scrub pythons and one by the spotted python. The sequence of the latter is an undescribed species phylogenetically related to S. lacertae. Of the two Sarcocystis species found in scrub pythons, one showed an 18S rRNA gene sequence similar to S. zamani, which is described from Australia for the first time. The second sequence was identical/similar to that of S. nesbitti, a known human pathogen that was held responsible for outbreaks of disease among tourists in Malaysia. The potential presence of S. nesbitti in Australia challenges the current hypothesis of a snake-primate life cycle, and would have implications for human health in the region. Further molecular and biological characterizations are required to confirm species identity and determine whether or not the Australian isolate has the same zoonotic potential as its Malaysian counterpart. Finally, the absence of S. nesbitti in samples from reticulated pythons (which were reported to be definitive hosts), coupled with our phylogenetic analyses, suggest that alternative snake hosts may be responsible for transmitting this parasite in Malaysia.

Coumarin derivatives have been in world-wide use for rodent pest control for more than 50 years. Due to their retarded action as inhibitors of blood coagulation by repression of the vitamin K reductase (VKOR) activity, they are the rodenticides of choice against several species. Resistance to these compounds has been reported for rodent populations from many countries around the world and poses a considerable problem for efficacy of pest control.

A field and a household survey, the latter of which included inspections and interviews with the residents of a total of 1370 properties, were conducted in 2004 in 30 villages of the city of Luang Prabang, Lao PDR, in order to assess the degree of rodent infestation and to identify potential factors influencing infestations. Roof rats, Rattus rattus, and the Polynesian rat, Rattus exulans, were the only rodents found in the city, and trapping results showed a clear dominance of roof rats (80–90% of all individuals). Measurements of rodent activity using tracking patches correlated positively with the trapping data, and revealed a significantly higher degree of rat infestation during the rainy season (September) than during the dry season (November). If households in the vicinity of the sampling locations were considered, villagers' accounts of indoor rodent infestations recorded during the household survey correlated positively with measurements of rodent activity. At least every second household reported indoor infestations. Using explorative statistical analyses (classification trees, factor analysis) we checked the predictive or explanatory value of up to 28 variables assessed during household inspections for villagers' observations on rodent infestation as the dependent variable. Trophic factors such as exposed food (indoors) and garbage (outdoors), and structural features such as open ceilings (indoors) and rat harborage in gardens (outdoors) ranked highest as explanatory variables. Assessment of a small sample of roof rat droppings collected inside houses revealed the presence of the potential disease agents Salmonella javiana, Cryptosporidium parvum, Giardia duodenalis and the parasitic nematode Calodium hepaticum (syn. Capillaria hepatica). These results underline the need for an appropriate rodent management strategy for the city, whereby simple sanitation and rodent‐proofing measures could be cheap means of reducing rat infestation rates.