Parasitic Infections in Wild Americas' Mammals: An Overview

Jim Crocker
7th March, 2024

Parasitic Infections in Wild Americas' Mammals: An Overview

Image Source: Natural Science News, 2024

Key Findings

  • Only 11 out of 35 American countries have data on Hepatozoon parasites in wild mammals
  • Carnivores and rodents are most studied; bats, hoofed animals, and shrews least known
  • Two main Hepatozoon groups found: one infects small mammals and the other infects carnivores
Understanding the complex relationships within ecosystems, particularly those involving parasites, is crucial for grasping how diseases spread and evolve. A recent comprehensive review by researchers at the Universidad de Concepción[1] has shed light on the state of knowledge concerning Hepatozoon parasites in wild mammals across the Americas. Hepatozoon species are protozoan parasites that infect a variety of vertebrates and rely on blood-feeding invertebrates, like ticks, to complete their life cycle. This review is timely, considering the last extensive examination of Hepatozoon occurred over a quarter-century ago. Since then, there hasn't been a concerted effort to harmonize data on the epidemiology, diagnostic methods, genetic diversity, and evolutionary relationships of these parasites in the Americas. The study aimed to provide a foundation for future research by consolidating existing information using the PRISMA method, a systematic approach for identifying, evaluating, and summarizing research. The findings of the review revealed that out of 35 countries in the Americas, only 11 (31.4%) had data on Hepatozoon infections in wild mammals. The orders Carnivora (which includes dogs, cats, and bears) and Rodentia (such as mice and squirrels) were the most frequently studied, while bats, ungulates (hoofed animals), and shrews had the least amount of data. Several species of Hepatozoon were identified, but many genospecies—distinct genetic groups that are not yet formally described as species—remain to be characterized through a combination of genetic and morphological analysis. The study also highlighted that the vectors for Hepatozoon, which are the invertebrates responsible for transmitting the parasite between hosts, are largely unidentified in the Americas. However, some flea, mite, and tick species have been confirmed as carriers. To date, detection of Hepatozoon has predominantly used conventional polymerase chain reaction (PCR), a technique that amplifies DNA to identify the presence of the parasite. The researchers suggest that employing specific real-time PCR methods could enhance the diagnosis of Hepatozoon infections in wild animals. From a genetic standpoint, the review found that the V4 region of the 18S rRNA gene is commonly sequenced to identify Hepatozoon species. However, to fully distinguish between species, the study recommends targeting mitochondrial and apicoplast markers—components of the cell that contain their own genetic material. Phylogenetic analysis, which is a method used to infer evolutionary relationships, of the 18S rDNA sequences collected showed two main groups, or clades, of Hepatozoon. Clade I is associated with small mammals, birds, and reptiles/amphibians (herpetozoa), while Clade II primarily includes carnivores. This division is also reflected in the haplotype network, which is a representation of the genetic relationships between individual organisms. The review underscores the importance of Hepatozoon as a potential disease agent in threatened wild mammals. It also points out the role of wild canids, such as the domestic dog and its wild relatives, as spreaders of Hepatozoon infections. The hybridization between wild canids and domestic dogs[2] could further complicate the dynamics of disease transmission, as it may lead to increased opportunities for the spread of parasites like Hepatozoon. Moreover, the review's findings echo the need for vigilance in monitoring tick-borne diseases in wild and domestic animals, as evidenced by the presence of tick-transmitted protozoa in felids[3] and cervids[4], as well as the detection of tick-borne pathogens in small mammals and ticks in Canada[5]. These studies collectively highlight the intricate web of interactions between hosts, vectors, and parasites, and the potential for disease spread beyond current geographical boundaries. In conclusion, the comprehensive review provides a much-needed update on Hepatozoon parasites in the Americas and sets the stage for future research. It is a call to action for more extensive and harmonized studies that can help protect wildlife health and biodiversity, as well as inform conservation efforts and disease management strategies for wild mammals across the continent.

WildlifeEcologyAnimal Science


Main Study

1) Hepatozoon (Eucoccidiorida: Hepatozoidae) in wild mammals of the Americas: a systematic review.

Published 6th March, 2024

Related Studies

2) Hybridization in Canids-A Case Study of Pampas Fox (Lycalopex gymnocercus) and Domestic Dog (Canis lupus familiaris) Hybrid.

3) Molecular survey of Cytauxzoon spp. and Hepatozoon spp. in felids using a novel real-time PCR approach.

4) A search for piroplasmids and spirochetes in threatened pudu (Pudu puda) and associated ticks from Southern Chile unveils a novel Babesia sp. and a variant of Borrelia chilensis.

5) Emerging Tick-Borne Pathogens in Central Canada: Recent Detections of Babesia odocoilei and Rickettsia rickettsii.

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