The Piroplasmida Babesia, Cytauxzoon, and Theileria in farm and companion animals: species compilation, molecular phylogeny, and evolutionary insights

Abstract

The order Piroplasmida, including the genera Babesia, Cytauxzoon, and Theileria is often referred to as piroplasmids and comprises of dixenous hemoprotozoans transmitted by ticks to a mammalian or avian host. Although piroplasmid infections are usually asymptomatic in wild animals, in domestic animals, they cause serious or life-threatening consequences resulting in fatalities. Piroplasmids are particularly notorious for the enormous economic loss they cause worldwide in livestock production, the restrictions they pose on horse trade, and the negative health impact they have on dogs and cats. Furthermore, an increasing number of reported human babesiosis cases are of growing concern. Considerable international research and epidemiological studies are done to identify existing parasite species, reveal their phylogenetic relationships, and develop improved or new drugs and vaccines to mitigate their impact. In this review, we present a compilation of all piroplasmid species, isolates, and species complexes that infect domestic mammals and which have been well defined by molecular phylogenetic markers. Altogether, 57 taxonomic piroplasmid entities were compiled, comprising of 43 piroplasmid species, 12 well-defined isolates awaiting formal species description, and two species complexes that possibly mask additional species. The extrapolation of the finding of at least 57 piroplasmid species in only six domestic mammalian groups (cattle, sheep, goat, horse, dog, and cat) allows us to predict that a substantially higher number of piroplasmid parasites than vertebrate host species exist. Accordingly, the infection of a vertebrate host species by multiple piroplasmid species from the same and/or different phylogenetic lineages is commonly observed. Molecular phylogeny using 18S rRNA genes of piroplasmids infecting domestic mammals results in the formation of six clades, which emerge due to an anthropocentric research scope, but not due to a possibly assumed biological priority position. Scrutinizing the topology of inferred trees reveals stunning insights into some evolutionary patterns exhibited by this intriguing group of parasites. Contrary to expectations, diversification of parasite species appears to be dominated by host-parasite cospeciation (Fahrenholz's rule), and, except for piroplasmids that segregate into Clade VI, host switching is rarely observed. When only domestic mammalian hosts are taken into account, Babesia sensu lato (s.l.) parasites of Clades I and II infect only dogs and cats, respectively, Cytauxzoon spp. placed into Clade III only infect cats, Theileria placed into Clade IV exclusively infect horses, wheras Theileria sensu stricto (s.s.) of Clade V infects only cattle and small ruminants. In contrast, Babesia s.s. parasites of Clade VI infect all farm and companion animal species. We outline how the unique ability of transovarial transmission of Babesia s.s. piroplasmids of Clade VI facilitates species diversification by host switching to other host vertebrate species. Finally, a deterioration o...

Babesiosis in Southeastern, Central and Northeastern Europe: An Emerging and Re-Emerging Tick-Borne Disease of Humans and Animals

“…In addition, the two piroplasms are closely related and some molecular diagnostic assays fail to distinguish between isolates of T. equi and Babesia spp. While other Theileria species are known to exist in wild animals, such as deer and boars, these do not pose a threat to human populations or our domestic animals in the region of Europe that is covered in our review [ 29 ]. Therefore, in the current review, we summarize recent findings on the occurrence and incidence of babesiosis in southeastern, central, and northeastern Europe (Bosnia and Herzegovina, Croatia, Serbia, Austria, Luxembourg, Switzerland, Germany, Hungary, the Czech Republic, Slovakia, Slovenia, Poland, Lithuania, Latvia, Estonia, Iceland, Denmark, Finland, Sweden, and Norway), in humans and selected species of domesticated animals (cats, dogs, horses, and cattle), and T. equi in horses.…”

Molecular Survey and Genetic Characterization of Anaplasma marginale in Ticks Collected from Livestock Hosts in Pakistan

“…Anaplasma species (Anaplasmataceae: Rickettsiales) are obligate intracellular Gramnegative bacteria transmitted by ticks to animal hosts, including humans, that can propagate and survive within the host cells [8][9][10]. Tick genera such as Rhipicephalus, Haemaphysalis, Dermacentor, Amblyomma, and Ixodes transmit Anaplasma spp.…”

Unraveling the Complexity of the Rhomboid Serine Protease 4 Family of Babesia bovis Using Bioinformatics and Experimental Studies

“…Babesia bovis is a highly pathogenic tick-transmitted apicomplexan protozoon causing bovine babesiosis, which affects the welfare and productivity of cattle in vast tropical and subtropical regions of the world [ 1 , 2 , 3 ].…”

“…In the case of B. bovis, Rhipicephalus microplus is the most common vector worldwide [ 5 ]. In the vertebrate bovine host, B. bovis , pertaining to Babesia sensu stricto (Clade VI) [ 2 , 3 ], thrives and divides exclusively within erythrocytes by merogony. During a blood meal on an infected animal, parasitized erythrocytes are ingested by ticks, and in the tick’s gut, parasites are released and transformed into characteristic isogametic ray bodies.…”

“…Upon kinete invasion of the epithelial cells of the tick salivary glands, additional sporogony results in the production of a large quantity of infective sporozoites. Sporozoites are injected with tick saliva into the bovine dermis upon a blood meal, reach the capillaries, invade erythrocytes and undergo asexual merogony, closing the cycle [ 3 , 4 , 6 ].…”