GENETIC DIVERSITY OF Sarcoptes scabiei IN PERUVIAN CAMELIDS: time -based comparison by microsatellite analysis

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إنجليزي. INTRODUCTIONSarcoptic mange, caused by the mite Sarcoptes scabiei, is one of the most important diseases in South American camelids, affecting both the domestic species, llama (Lama glama) and alpaca (Vicugna pacos), and the wild species, vicuña (Vicugna vicugna) and guanaco (Lama guanicoe). In the domestic species, the disease causes notable economic losses due to the affectation of fiber and leather, and to mortality, to a lesser degree (Beltrán-Saavedra et al., 2011; Bujaico and Zuñiga, 2016). Alpacas from Marangani and Macusani are from different areas (Cusco and Puno respectively) and animals were never mixed.MATERIALS AND METHODSSamples from mangy alpacas were collected by skin scrapping from four different Peruvian locations during the years 2016, 2021 and 2022. The presence of S. scabiei was confirmed microscopically and mites were recovered and placed in 70% ethanol. DNA was extracted from individual mites following the HotSHOT Plus ThermalSHOCK technique (Alasaad et al., 2008). Nine mite microsatellite markers (SARMS 33, 35, 36, 37, 38, 40, 41, 44 and 45) (Rasero et al., 2010) were amplified in a multiplex PCR as described in (Moroni et al., 2021). PCR products were separated by electrophoresis using SeqStudio genetic Analyzer. Microsatellite fragment sizes and alleles were assigned with GeneMapperTM software. Micro-Checker 2.2.3 (Van Oosterhout et al. 2004) was used to detect the presence of null alleles. Standard genetic diversity parameters for microsatellite data, such as observed (Ho) and expected (He) heterozygosities, Hardy–Weinberg equilibrium, number of alleles and number of private alleles were calculated using Arlequin 3.5 software (Excoffier and Lischer, 2010).To test for genetic differentiation among mites from different locations a Bayesian clustering analysis was performed with STRUCTURE program (Pritchard et al., 2000) using a burn-in period of 100,000 followed by the same number of MCMC replication. The number of populations (K) was varied from 1 to 6 and the assignment of the most probable K was made taking into account the maximum value of ln [Pr (X / K)] (Evanno et al., 2005).RESULTSThe observed (Ho) and expected (He) heterozygosity across all loci were 0.22814 and 0.50105 respectively and all of the loci were polymorphic, considering the whole data set. The number of alleles per locus ranged from 1 (SARMS36 for Macusani, Huanuco and Puno) to 7 (SARMS33 for Macusani) with a total number of 46 observed alleles. All locations presented privates alleles for at least one locus. Additionally, Macusani presented the highest values for most diversity parameters, followed by Huanuco. This result is maintained when a correction for sample size is applied, as can be seen for AR values. AMOVA analysis showed the highest percentage of variance to occur among samples (54.75%) rather than within them (45,25%). Deviations from Hardy–Weinberg equilibrium were detected for some loci in Macusani, Huanuco and Puno locations, however results from Micro-Checker, suggested the presence of null alleles in those loci. Bayesian cluster analysis with the software STRUCTURE using the method of Evanno established that the number of clusters that best fit the data is K=2. Mites from Marangani, Macusani and Huanuco were grouped into a single cluster, while Puno conforms a different genetic cluster. Furthermore, two mites from Puno, from different alpaca individuals, showed mixed ancestry. CONCLUSIONMites from the mange outbreak of Puno 2021 have a different genetic composition than the ones from Macusani 2016, therefore it is likely that these two outbreaks have originated from different sources. Mites from Marangani, Macusani and Huanuco seems to have similar genetic composition. However, alpacas from Marangani and Macusani are from distant areas and animals were never mixed, a substructure could be present within this cluster though the number samples and markers should be increase in order to detect it.Further investigations, including other domestic species are required to fully understand the spread of sarcoptic mange in alpaca populations and would help to implement efficient disease control mechanisms and sanitary management.