First report of Toxoplasma gondii sporulated oocysts and Giardia duodenalis in commercial green-lipped mussels (Perna canaliculus) in New Zealand

Abstract

Pollution of marine ecosystems with the protozoan parasites Toxoplasma gondii, Cryptosporidium spp. and Giardia duodenalis can be studied using bivalve shellfish as biosentinels. Although evidence suggests that these parasites are present in New Zealand coastal waters, the extent of protozoal pollution has not been investigated. This study used optimised molecular methods to detect the presence of Cryptosporidium spp., G. duodenalis and T. gondii in commercially sourced green-lipped mussel (Perna canaliculus), an endemic species found throughout coastal New Zealand. A nested polymerase chain reaction was validated for detection of T. gondii DNA and applied to 104 commercially sourced mussels. Thirteen mussels were positive for T. gondii DNA with an estimated true prevalence of 16.4% using Bayesian statistics, and the presence of T. gondii in mussels was significantly associated with collection during the summer compared with that in the winter (P = 0.003). Consumption of contaminated shellfish may also pose a health risk for humans and marine wildlife. As only sporulated T. gondii oocysts can be infectious, a reverse transcriptase-polymerase chain reaction was used to confirm presence of a sporozoite-specific marker (SporoSAG), detected in four mussels. G. duodenalis assemblage B, known to be pathogenic in humans, was also discovered in 1% mussels, tested by polymerase chain reaction (n = 90). Cryptosporidium spp. was not detected in the sampled mussel haemolymph. Results suggest that New Zealand may have high levels of coastal contamination with T. gondii, particularly in summer months, and that naturally exposed mussels can ingest and retain sporulated oocysts, further establishing shellfish consumption as a health concern.

Molecular Epizootiology of Toxoplasma gondii and Cryptosporidium parvum in the Eastern Oyster (Crassostrea virginica) from Maine (USA)

“…Interestingly, DNA metabarcoding of microbial eukaryotes in water samples collected from the same areas did not reveal the presence of either protozoan parasite outside of oyster hosts (N.D.M., N.R.R., P.D.C., J.A.F.R., unpublished data). The presence of sporulated T. gondii oocysts in commercial green-lipped mussels ( Perna canaliculus ) from New Zealand has been recently reported via Reverse Transcriptase-PCR (RT-PCR) [48]; but whether the oocysts of both T. gondii and C. parvum could have excysted remains an open question. We used species-specific qPCR assays to target the presence and abundance of protozoan DNA in oyster tissues.…”

“…We used species-specific qPCR assays to target the presence and abundance of protozoan DNA in oyster tissues. As only sporulated T. gondii and C. parvum oocysts can be infectious, an RT-PCR targeting a sporozoite-specific marker (e.g., SporoSAG for T. gondii ) [48] from active cells would be required to assess the potential risk of infection for human consumption. In the case of C. parvum , even if the excystment happens, the complexity of this parasite [49] makes infection from oyster cells very unlikely.…”

“…Our survey relied on qPCR detection of DNA extracted from oyster tissues, and the results could well be an indication that T. gondii oocysts are also passing through the bivalve [54,55]. Establishing the risk of Toxoplasma infection from eating raw bivalves [48] would require the development and validation of methods for the detection and survival/infectivity assays to enable robust risk assessments and implementation of control measures [2].…”

Aquatic disease in New Zealand: synthesis and future directions

“…Fish parasites, like the bacterium Edwardsiella tarda, the cause of piscine septicaemia, have been reported overseas as introduced to the sea from wastewater (Mohanty and Sahoo 2007). Toxoplasma gondii is a common terrestrial parasite that uses felines as a definitive host and recently T. gondii has been identified in GLM (Coupe et al 2018) and five New Zealand marine mammals (Lehnert et al 2019), most notably Hector's dolphins (Roe et al 2013). Globally, the detection of T. gondii has sparked concerns about the role T. gondii has in the health of different aquatic animals, particularly the endangered southern sea otter (Enhydra lutris nereis) (Miller et al 2002).…”

Detección de ooquistes de Cryptosporidium parvum (Apicomplexa: Cryptosporidiidae) en ejemplares de cholga Aulacomya ater, extraídas desde la costa de la Región del Bío Bío, Chile

“…Durante este proceso, los moluscos pueden retener microorganismos patógenos tales como bacterias, virus y protozoos presentes en el ambiente, los que se adhieren en el mucus secretado en esta estructura, o bien, pueden pasar hacia su tracto digestivo, acumulándose a lo largo del tiempo 1 . Algunos autores han reportado la presencia de distintos protozoos patógenos en bivalvos de aguas dulce y/o salada [2][3][4][5] , dentro de los cuales se ha identificado la presencia del coccidio intestinal Cryptosporidium sp., patógeno oportunista del ser humano.…”