Ticks are significant ectoparasites of humans, domestic and wild animals (Jongejan and Uilenberg, 1994); and are distributed globally in different environmental conditions. They have a considerable importance in the medical and veterinary health as they harbor and transmit a wide range of pathogens causing diseases to their preferred hosts (Jongejan and Uilenberg, 1994; Dantas-Torres, 2010). Nuttalliellidae was an ancient monotypic tick family from the order Ixodida, which also comprises of Argasidae, Ixodidae as well as the three extinct fossil families Deinocrotonidae (Peñalver et al., 2017), Khimairidae (Chitimia-Dobler et al., 2022) and Legionaris (Chitimia-Dobler et al., 2024), which were described recently based on fossil tick specimens from Burmese amber deposits. At present, approximately 970 extant tick species have been described globally and Ixodidae is the largest and most prominent with ~750 species, followed by Argasidae with ~218 species, while Nuttalliellidae has a sole extant genus and species, Nuttalliella and Nuttalliella namaqua (Dantas-Torres and Otranto, 2022), as well as five extinct species, namely, Nuttalliella gratae sp. nov., Nuttalliella odyssea sp. nov., Nuttalliella placaventrala sp. nov., Nuttalliella tropicasylvae sp. nov. and Nuttalliella tuberculata sp. nov., that were described and placed within the genus Nuttalliella (Chitimia-Dobler et al., 2024). Deinocrotonidae had one species as well, however, an additional species has been described along with the fossil family Khimairidae (Chitimia-Dobler et al., 2022) and two more species described recently from Burmese fossil deposits as well (Chitimia-Dobler et al., 2024). Moreover, the above-mentioned authors also reported that the notable similarities between the genera Nuttalliella, Deinocroton and the newly described Legionaris justifies the addition of the latter two genera in the family Nuttalliellidae besides Nuttalliella. Even though ticks are ranked second to mosquitoes as vectors of the bacterial, protozoan and viral disease-causing pathogens of animals and humans (Jongejan and Uilenberg, 1994; Parola and Raoult, 2001), the potential of N. namaqua being a vector is still not established; and it has not been associated to any pathogen/disease since its description.

The acknowledged names (Nuttalliellidae and Nuttalliella) for this family and genus were given as an honor to George Nuttall, the bacteriologist who was a notable specialist in tick-borne diseases (Bedford, 1931). The species name is however given based on the collection site (Kamieskroon, in Little Namaqualand) of the first specimen described as N. namaqua (Bedford, 1931). The above-mentioned author (Bedford, 1931) also hypothesized that this species is a significant link that has been missing in the evolutionary chain of the families Argasidae and Ixodidae. In addition, it is also shown to be closely related to the genus Ixodes (Bedford, 1931) as well as the fossil family Deinocrotonidae (Peñalver et al., 2017), however, its life cycle is still not certainly documented. Interestingly, despite the first specimen of N. namaqua tick species being described over 90 years ago; its life cycle and the natural hosts of all the life stages are still not certainly defined. Thus, the focus of this review was to answer the following proposed questions (i) What is the distribution of the genus Nuttalliella? (ii) Is the species collected from all those countries similar or is there any variation between them? (iii) Is it occurring in minimal or abundant but under documented? (iv) What are its natural preferred hosts? (v) What is the relationship between Nuttalliellidae and other families?

In reference to the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines for scoping reviews (PRISMA-ScR) (Tricco et al., 2018), a search of literature was conducted by both authors (LMB; DPM) independently in Google Scholar and PubMed databases. Boolean operators were used to combines the search terms and the search criteria for both the databases included the key search terms such as: Nuttalliella [AND] occurrence; Nuttalliella namaqua [AND] distribution; Nuttalliella namaqua [AND] hosts; Nuttalliella namaqua [AND] life cycle; Nuttalliellidae [AND] Argasidae [AND] Ixodidae; Nuttalliella namaqua [OR] Nuttalliella species [AND] Africa (Algeria [OR] Angola [OR] Benin [OR] Botswana [OR] Burkina Faso [OR] Burundi [OR] Cameroon [OR] Cape Verde [OR] Central African Republic [OR] Chad [OR] Comoros [OR] Congo [OR] Côte d’lvoire [OR] Djibouti [OR] DR Congo [OR] Egypt [OR] Equatorial Guinea [OR] Eritrea [OR] Ethiopia [OR] Gabon [OR] Gambia [OR] Ghana [OR] Guinea [OR] Guinea-Bissau [OR] Kenya [OR] Lesotho [OR] Liberia [OR] Libya [OR] Madagascar [OR] Malawi [OR] Mali [OR] Maurinatia [OR] Mauritius [OR] Morocco [OR] Mozambique [OR] Namibia [OR] Niger [OR] Nigeria [OR] Réunion [OR] Rwanda [OR] Sao Tome and Principe [OR] Senegal [OR] Seychelles [OR] Sierra Leone [OR] Somalia [OR] South Africa [OR] South Sudan [OR] Sudan [OR] Swaziland [OR] Tanzania [OR] Togo [OR] Tunisia [OR] Uganda [OR] Western Sahara [OR] Zambia [OR] Zimbabwe). Additional literature searches were done by assessing the references of the initial search output and all the results were filtered and screened by respectively removing the duplicates and reviewing the titles and abstracts. Full text of the articles deemed relevant were downloaded and assessed for eligibility by both authors (LMB; DPM).

The eligibility criteria used in this review, more especially the long range of publication time-limit (1920 to January 2024), was considered because definite insights on the family Nuttalliellidae are still not clearly established; despite the initial species of this family being described more than 90 years ago. Thus, eligibility of the downloaded full text was assessed following the established inclusion criteria which briefly include: (a) Articles published in peer-reviewed journals reporting on the distribution of N. namaqua as well as the occurrences and descriptions of Nuttalliella species; (b) Articles published from 1920 to at present; (c) Articles that clearly state the tests used in the study; as well as (d) Articles with sample information clearly indicated and described. References that were excluded in the review include: (a) Theses and books; (b) Articles that only mention but do not report on the occurrence, description or distribution of Nuttalliella; (c) All types of review articles; (d) Studies that do not contribute towards answering the research questions.

Data was extracted from the included articles and the following information was recorded and used for further appraisal: article authors, sex and life-cycle stage of the collected N. namaqua ticks, host or source, geographical localities, diagnostic tests used for screening, outcomes of the included studies. Data was appraised and analyzed using Excel 2016.

The current review has shown that N. namaqua has a distribution that is limited to African regions that include Botswana (Apanaskevich, 2021), Namibia (Keirans et al., 1976; Apanaskevich, 2021), Mozambique (Apanaskevich, 2021), South Africa (Bedford, 1931; Keirans et al., 1976; Horak et al., 2012; Latif et al., 2012; Stevens et al., 2022) and Tanzania (Keirans et al., 1976). Ticks are distributed globally; however, the distribution of specific tick species varies based on the biotic and abiotic factors such as presence of hosts, vegetation types, altitude, rainfall, humidity and temperature (Jongejan and Uilenberg, 1994). In the southern African region, the distribution range of N. namaqua appears to be in arid and semi-arid localities except in Tanzania. It is presumed that the fact that N. namaqua species are mainly collected and confined in limited southern African localities, might be an indication that Ixodidae may have originated in Africa (Mans et al., 2011, 2012). In addition, the species shows preference to habitats such as rocky areas, mixed trees and shrub savannah biome (Mans et al., 2011).

The recent description of new Nuttalliella species from the fossil specimens collected from the Burmese amber deposits shows that it is probable that the distribution of this genus might also include the Antarctica and Australia (Chitimia-Dobler et al., 2024). This corresponds with the theories of Barker et al. (2014), who speculated that the family Nutalliellidae may have occurred in Australia before the extinction of their preferred hosts, and/or some extant species might still be there but not discovered yet. However, we hypothesize that it might not be the case with the distribution of the extant N. namaqua since it was not among the newly described fossil Nuttalliella species that has been collected outside the known African regions. On the other hand, further investigations and discovery of this species might provide more insight on its distribution like in the case of Ixodes scapularis, which was known to have a distribution limited to the south-eastern United States until it was established that it is a vector of Borrelia burgdorferi, the causal agent of Lyme disease in humans (Eisen and Eisen, 2023). Additionally, only 12 articles were included and appraised in the review and the low number of the articles included and appraised in this review might be due to the fact that the species N. namaqua is scarce; thus, resulting in low collection rate and/or it is under-investigated or under-reported. This is also shown by the period between the first collection and description of this species (Bedford, 1931) and its second report (Keirans et al., 1976).

The life cycle of all tick species involves four development phases such as the egg, larval, nymphal and adult stages, which varies based on the genus and/or species (Saleh et al., 2021). Despite Nuttalliella being an ancient genus, its life cycle is still not clear; and it took more than 80 years before the first specimen of larva and males were collected and described. Thus, due to the abovementioned fact, there were speculation that N. namaqua species are parthenogenic, or the males are reserved, or the gender ration of this species is inordinate (Oliver, 1989; Latif et al., 2012). Males were described from the two pairs of ticks that were found in a mating position at different times from Springbok, Namaqualand in South Africa and were later confirmed to be male and female respectively (Latif et al., 2012).

Host preference is generally different among ticks, and it is crucial for tick survival as the extinction of a preferred host can result in the dying out of ticks that cannot be accustomed to the available host (Koh et al., 2004). In case of N. namaqua, the current review has shown that the host preference of other life stages except the larva (Horak et al., 2012; Apanaskevich, 2021; Stevens et al., 2022), has not been clearly described. Numerous studies (Keirans et al., 1976; El Shoura et al., 1984; Oliver, 1989) have also shown that the preferred natural host of this species is still uncertain. However, Mans et al. (2012) reported that N. namaqua appears to be a generalist since it has been collected from various mammalian hosts, and further investigation of the gut meal from a field collected nymphs and females indicated that they have fed from different lizard species. The above authors (Mans et al., 2012) also speculated that the species has the ability to switch hosts numerously in case of possible extinctions of the preferred hosts. In another study, Horak et al. (2012) has reported that murid rodents are natural hosts of N. namaqua larva. Moreover, the authors (Horak et al., 2012) also showed that none of the elephant shrews and hedgehogs found in the same area and examined together with the rodents was infested. Conforming with Horak et al. (2012), a recent study (Apanaskevich, 2021) also collected a large number of larvae from murid rodents and morphologically identified them as N. namaqua. Moreover, murid rodents have also been reported as the preferred host of immature stages of several ixodid ticks and ectoparasites in general (Petney et al., 2004; Matthee et al., 2010; Stevens et al., 2022).

Still, the natural hosts parasitized by nymphs of this species are still not known. El Shoura (1991) reported an unsuccessful feeding of nymphs and females on mice, rats, pigeons, chickens and rabbits attempted in the laboratory to further verify the host preference of N. namaqua. While Mans et al. (2011) reported their (nymphs and females) successful feeding on lizard in a laboratory setup as well. Numerous specimens were collected off the hosts in localities such as abundant bird nests, on the ground, under the rocks or in the rock crevices (Mans et al., 2011, 2012). This might be because N. namaqua can survive for a longer period off-host and without feeding as it can store hemoglobin and red blood cells longer owing to its rapid feeding as well as the slow digestion behavior (Latif et al., 2012). Hence, it has been collected off-host at secluded collection sites that include under a stone, nests of birds as well as the rock crevice, which are habitats of their possible hosts. Thus, allowing the ticks to concurrently quest and be protected from poor climatic conditions.

Even though it is almost a century since the initial description of Nuttalliellidae, this review shows that its lifecycle is still not completely established, and the distribution of the extant N. namaqua is still limited to a few African countries. Most adult ticks were collected in South Africa, with only a few from Namibia and Tanzania. Even though it combines some features of both the Argasidae and Ixodidae, it also possesses its unique characteristics. Nuttalliella namaqua is also not linked to any disease-transmitting pathogen since its description. Limited knowledge of the family Nuttalliellidae as well as the recently described fossil families Deinocrotonidae, Khimairidae and Legionaris extend the gap and hinder the advances in determining the tick phylogeny and ancestral lineage.

The original contributions presented in the study are included in the article/supplementary material, further inquiries can be directed to the corresponding author/s.

ML: Writing – original draft, Writing – review & editing, Conceptualization, Data curation, Formal analysis, Methodology, Project administration, Validation. DM: Writing – original draft, Writing – review & editing, Conceptualization, Data curation, Methodology, Project administration, Resources, Supervision, Validation.