Prevalence and genotype of Toxoplasma gondii in stranded Hawaiian cetaceans

Abstract

Toxoplasma gondii is a significant threat to endangered Hawaiian wildlife including birds and marine mammals. To estimate the prevalence of T. gondii in stranded cetaceans from 1997 to 2021 in Hawai‘i, we tested tissues from 37 stranded spinner dolphins Stenella longirostris and 51 stranded individuals that represented 18 other cetacean species. DNA from cetacean tissue extracts were screened using a nested polymerase chain reaction (PCR) assay targeting the Toxoplasmatinae internal transcribed spacer 1 of the nuclear ribosomal DNA. A positive result was obtained in 9 tissues examined for each of 2 spinner dolphins out of 525 tissue samples analyzed by PCR. The PCR-positive spinner dolphins had disseminated acute toxoplasmosis with necrosis, inflammation, and intralesional protozoal cysts and tachyzoites in multiple organs. Discrete positive immunostaining for T. gondii was observed in all tissues tested including the adrenal gland, brain, liver, and lung. Both positive spinner dolphins were negative for cetacean morbillivirus. The T. gondii genotyping was performed by restriction fragment length polymorphism (PCR-RFLP) based on 10 genetic markers. The PCR-RFLP analysis revealed the T. gondii belonged to PCR-RFLP-ToxoDB genotype #24, previously detected in wild pig Sus scrofa in O‘ahu, bobcats Lynx rufus from Mississippi, USA, and chickens Gallus gallus from Costa Rica and Brazil. These cases represent the first report of this genotype in aquatic mammals and the second and third reports of fatal disseminated T. gondii infection in stranded spinner dolphins from Hawai‘i. Nearshore species, like spinner dolphins, may be at increased risk of mortality from this parasite in marine coastal waterways via sewage systems, storm water drainage, and freshwater runoff.

Targeted surveillance detected novel beaked whale circovirus in ten new host cetacean species across the Pacific basin

“…Brucella was present in several of the tissues of the neonate sperm whale and likely the pathology observed, and an alpha herpesvirus was also described in the initial Longman's beaked whale, making both of these cases tri-infections (West et al, 2013;West et al, 2015). The individuals with BWCV and confirmed co-infections had respiratory disease, lymphoid depletion and poor body condition indicative of wasting (Landrau-Giovannetti et al, 2020;Landrau-Giovannetti et al, 2022;West et al, 2021). Conversely, other positive cases had no apparent pathology observed.…”

“…In addition to morbillivirus, an alpha herpesvirus was present in the Longman's beaked whale and Brucella ceti in the neonate sperm whale (West et al, 2013;West et al, 2015). Disseminated toxoplasmosis was diagnosed in an adult male spinner dolphin (Landrau-Giovannetti et al, 2022). A presumed healthy pelagic false killer whale in robust body condition that was by-caught outside of the Exclusive Economic Zone off Hawai'i tested positive for BWCV, but did not show signs of systemic disease.…”

“…Cetacean morbillivirus, a potentially fatal disease, was found in four of the BWCV cases from the Pacific Islands, including the initial Longman's beaked whale case, as well as a neonate sperm whale, a subadult Blainville's beaked whale, and a Fraser's dolphin infected with a novel morbillivirus strain (West et al, 2013;West et al, 2015;Jacob et al, 2016;West et al, 2021). Fatally disseminated toxoplasmosis was found in an adult spinner dolphin that was positive for BWCV (Landrau-Giovannetti et al, 2022). Brucella was present in several of the tissues of the neonate sperm whale and likely the pathology observed, and an alpha herpesvirus was also described in the initial Longman's beaked whale, making both of these cases tri-infections (West et al, 2013;West et al, 2015).…”

Identifying and Comparing Important Areas for Marine Sustainable Use and Conservation

“…Cetaceans in Hawaiian waters overlap with a number of anthropogenic activities that have the potential to result in both indirect and direct harmful population-level consequences. Threats include military operations (e.g., Martin et al, 2015;Henderson et al, 2019;Baird et al, 2021a;Durbach et al, 2021), commercial and recreational fishing (e.g., Baird and Webster, 2020;Baird et al, 2021b), tourism (e.g., Currie et al, 2021), shipping (e.g., Lammers et al, 2013), pollutants (e.g., Ylitalo et al, 2009;Bachman et al, 2014;Kratofil et al, 2020), protozoal disease from feral, non-native cats (Migaki et al, 1990;Landrau-Giovannetti et al, 2022), and marine debris (Currie et al, 2017). The range-resident behavior of many Hawaiian cetaceans (Baird, 2016) may further exacerbate risk from these threats; where site fidelity may have once been evolutionarily advantageous, this mechanism may become maladaptive in the Anthropocene (Merkle et al, 2022).…”

Biologically Important Areas II for cetaceans within U.S. and adjacent waters – Hawaiʻi Region

“…Cetaceans in Hawaiian waters overlap with a number of anthropogenic activities that have the potential to result in both indirect and direct harmful population-level consequences. Threats include military operations (e.g., Martin et al, 2015;Henderson et al, 2019;Baird et al, 2021a;Durbach et al, 2021), commercial and recreational fishing (e.g., Baird and Webster, 2020;Baird et al, 2021b), tourism (e.g., Currie et al, 2021), shipping (e.g., Lammers et al, 2013), pollutants (e.g., Ylitalo et al, 2009;Bachman et al, 2014;Kratofil et al, 2020), protozoal disease from feral, non-native cats (Migaki et al, 1990;Landrau-Giovannetti et al, 2022), and marine debris (Currie et al, 2017). The range-resident behavior of many Hawaiian cetaceans (Baird, 2016) may further exacerbate risk from these threats; where site fidelity may have once been evolutionarily advantageous, this mechanism may become maladaptive in the Anthropocene (Merkle et al, 2022).…”