This article provides generalized estimators for the random-coefficients panel data (RCPD) model where the errors are cross-sectional heteroskedastic and contemporaneously correlated as well as with the first-order autocorrelation of the time series errors. Of course, under the new assumptions of the error, the conventional estimators are not suitable for RCPD model. Therefore, the suitable estimator for this model and other alternative estimators have been provided and examined in this article. Furthermore, the efficiency comparisons for these estimators have been carried out in small samples and also we examine the asymptotic distributions of them. The Monte Carlo simulation study indicates that the new estimators are more efficient than the conventional estimators, especially in small samples.

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Avian coronaviruses (ACoVs) are continuously evolving and causing serious economic consequences in the poultry industry and around the globe. Owing to their extensive genetic diversity and high mutation rates, controlling ACoVs has become a challenge. In this context, the potential contribution of wild birds in the disease dynamics, especially in domesticated birds, remains largely unknown. In the present study, five hundred fifty-seven ( = 557) cloacal/fecal swabs were collected from four different wild bird species from eight Egyptian governorates during 2016 and a total of fourteen positive isolates were used for phylodynamics and evolutionary analysis. Genetic relatedness based on spike (S1) gene demonstrated the clustering of majority of these isolates where nine isolates grouped within Egy/variant 2 (IS/885 genotype) and five isolates clustered within Egy/variant 1 (IS/1494/06 genotype). Interestingly, these isolates showed noticeable genetic diversity and were clustered distal to the previously characterized Egy/variant 1 and Egy/variant 2 in Egyptian commercial poultry. The S1 gene based comparison of nucleotide identity percentages revealed that all fourteen isolates reported in this study were genetically related to the variant GI-23 lineage with 92⁻100% identity. Taken together, our results demonstrate that ACoVs are circulating in Egyptian wild birds and highlight their possible contributions in the disease dynamics. The study also proposes that regular monitoring of the ACoVs in wild birds is required to effectively assess the role of wild birds in disease spread, and the emergence of ACoVs strains in the country.

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