Report on Surveillance for Avian Influenza in Wild Birds

Wan-Chen Li

Abstract

The high pathogenicity H5N1 avian influenza virus was first discovered in geese in Guangdong in 1996. This lineage of virus has continued to spread and evolve, causing multiple severe outbreaks in the global poultry industry and posing threats to wildlife and public health. Migratory waterfowl are one of the transmission routes for introducing avian influenza viruses into Taiwan. Since 1998, Taiwan has been monitoring migratory wild waterfowl for avian influenza viruses. Initially, the main sample type was fecal droppings from waterfowl arriving in autumn and winter; after 2017, samples from dead and rescued birds were also included, without restrictions on species or seasonality. During the first 20 years of monitoring, nearly all detected viruses were low pathogenicity; however, starting from 2017, sporadic case of high pathogenicity avian influenza viruses were detected in dead birds (such as the black-faced spoonbill). After 2020, high pathogenicity avian influenza viruses began to be detected in fecal samples, with multiple cases continuing to be detected each autumn and winter thereafter. The introduction of next-generation sequencing technology in recent years has significantly increased the throughput for viral genome sequencing. Sequence analysis revealed that the H5N1 virus that invaded Taiwan include multiple genotypes. The trend of detecting H5N1 viruses in wild birds in Taiwan, along with the results of sequence analysis, reflects the widespread and ongoing transmission of these viruses globally and highlights the risks faced by the poultry industry during the autumn and winter seasons. The relevant results of this surveillance system can alert the poultry industry to improve biosecurity measures.

Case Report: protozoan parasite Marteilioides chungmuensis infection of portuguese oyster (Crassostrea angulata)

Chieh-Hao Wu

Abstract

Marteilioides chungmuensis is a protozoan parasite of oysters that can cause nodule-like growths in the ovaries and nutritional wasting in infected female oysters, potentially affecting their marketability due to appearance changes. In February 2023, M. chungmuensis was detected in farmed Portuguese oysters (Crassostrea angulata) from the southern coastal areas of Taiwan. Clinical signs included irregular nodule-like structures on the gonads (1/3 of cases) and extensive periphyton attached to the oysters. Histological examination revealed infected oocytes containing protozoan primary and secondary cells in their cytoplasm. The ovarian follicles were filled with distorted ova containing M. chungmuensis. PCR screening of the tissues using specific primer pairs confirmed the presence of M. chungmuensis. Based on the Basic Local Alignment Search Tool (BLAST), the 18S rDNA gene sequence showed the closest similarity (100% identity) to M. chungmuensis previously discovered in C. gigas and C. ariakensis. This study represents the first report of M. chungmuensis infection in farmed C. angulata in Taiwan.