SARS-CoV-2 Infection Dynamics in the Pittsburgh Zoo Wild Felids with Two Viral Variants (Delta and Alpha) during the 2021–2022 Pandemic in the United States

Abstract

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been reported in multiple animal species besides humans. The goal of this study was to report clinical signs, infection progression, virus detection and antibody response in a group of wild felids housed in adjacent but neighboring areas at the Pittsburgh Zoo. Initially, five African lions (Panthera leo krugeri) housed together exhibited respiratory clinical signs with viral shedding in their feces in March of 2021 coinciding with infection of an animal keeper. During the second infection wave in December 2021, four Amur tigers (Panthera tigris altaica) and a Canadian lynx (Lynx canadensis) showed clinical signs and tested positive for viral RNA in feces. In infected animals, viral shedding in feces was variable lasting up to 5 weeks and clinical signs were observed for up to 4 weeks. Despite mounting an antibody response to initial exposure, lions exhibited respiratory clinical signs during the second infection wave, but none shed the virus in their feces. The lions were positive for alpha variant (B.1.1.7 lineage) during the first wave and the tiger and lynx were positive for delta variant (AY.25.1. lineage) during the second wave. The viruses recovered from felids were closely related to variants circulating in human populations at the time of the infection. Cheetahs (Acinonyx jubatus) in the park did not show either the clinical signs or the antibody response.

Perspectives on SARS-CoV-2 Cases in Zoological Institutions

“…Although infections in both the European lynx (Lynx lynx) and Canadian lynx (Lynx canadensis) have been reported, only the Canadian lynx SARS-CoV-2 infections have been described in the peer-reviewed literature (n = 4) [20,31]. All of the infected animals were symptomatic, with clinical signs lasting between 17 and 35 days.…”

“…Lions ( Panthera leo ) represent the biggest group ( n = 37) of reported cases. Cases have been reported in both the Asiatic [ 36 , 37 , 38 , 39 ] and African subspecies [ 2 , 28 , 31 , 32 , 33 , 35 ]. The susceptibility of this species is underpinned by the infection of vaccinated (1.0 mL SQ or IM, Zoetis International, Parsippany, NJ, USA) animals and by reinfection of recovered animals [ 28 , 31 ].…”

“…Cases have been reported in both the Asiatic [ 36 , 37 , 38 , 39 ] and African subspecies [ 2 , 28 , 31 , 32 , 33 , 35 ]. The susceptibility of this species is underpinned by the infection of vaccinated (1.0 mL SQ or IM, Zoetis International, Parsippany, NJ, USA) animals and by reinfection of recovered animals [ 28 , 31 ]. Almost all (96.4%) cases were symptomatic, with symptoms lasting 14.8 days on average ( Table 2 ).…”

“…Almost all (96.4%) cases were symptomatic, with symptoms lasting 14.8 days on average ( Table 2 ). Although in one case, coughing was observed to persist for 49 days [ 31 ]. Coughing is reported in 81.5% of cases and is the most frequently observed clinical sign.…”

“…SARS-CoV-2 infections are relatively frequently observed in tigers ( n = 24) [ 2 , 28 , 31 , 34 , 37 , 41 , 42 , 43 , 44 ]. Similar to lions, infections have been reported in vaccinated (1.0 mL SQ or IM, Zoetis International) animals [ 28 ].…”