# New records of Hepatozoon and Oswaldofilaria from saltwater crocodiles (Crocodylus porosus) in Australia

## TL;DR

Researchers found new parasites in Australian saltwater crocodiles, suggesting these may be previously unknown species.

## Contribution

The study reports the first molecular analysis of haemoparasites in Australian saltwater crocodiles, identifying potential new species.

## Key findings

- Hepatozoon was detected in all wild and some captive crocodiles using microscopy and PCR.
- A filarial worm, likely Oswaldofilaria, was found in one captive crocodile.
- Phylogenetic analysis suggests the parasites may represent new species.

## Abstract

Diseases affecting wild Australian saltwater crocodiles (Crocodylus porosus) are rarely reported due to the difficulty in capturing animals and obtaining samples. In this investigation, we identified two haemoparasites (Hepatozoon and a filarial nematode) in saltwater crocodiles in Darwin, Australia. Light microscopic examination identified Hepatozoon in 7/7 (100%) wild crocodiles and in 2/20 (10%) of captive ones. When genomic DNAs from these same samples were further investigated using polymerase chain reaction (PCR)-based sequencing, we detected Hepatozoon in all 27 blood samples. Using both microscopy and PCR-based sequencing, we detected a filarial worm (proposed to be Oswaldofilaria) in one of 20 captive crocodiles. The sequence data were compared with sequence data available in public databases, and phylogenetic analyses indicated that the operational taxonomic units of Hepatozoon and Oswaldofilaria discovered here in these crocodiles are likely new species. This study is the first to use molecular tools to explore haemoparasites in Australian saltwater crocodiles and highlights the importance of health investigations in poorly studied vertebrate hosts.

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•Both wild and captive crocodiles were found to be infected with a Hepatozoon sp.•A single captive crocodile was found to infected with an Oswaldofilaria sp.•Molecular analysis of parasites suggests that they are likely to be novel species.•Pathogenicity, and lifecycle of these parasites in crocodiles are still unknown.

Both wild and captive crocodiles were found to be infected with a Hepatozoon sp.

A single captive crocodile was found to infected with an Oswaldofilaria sp.

Molecular analysis of parasites suggests that they are likely to be novel species.

Pathogenicity, and lifecycle of these parasites in crocodiles are still unknown.