Gastrointestinal parasite diversity of South American camelids (Artiodactyla: Camelidae): First review throughout the native range of distribution

In South America inhabit an endemic group of ungulates adapted to extreme environments: the South American camelids (SAC), a key component of the Andean biocultural heritage. Until today, SAC are the most important factor of Andean economies and social and ritual life. SAC include two wild species, the guanaco (Lama guanicoe) and the vicuña (Vicugna vicugna), and two domestic species, the llama (Lama glama) and the alpaca (Vicugna pacos). Endoparasitosis are one of the most common diseases in SAC, and have great economic and health relevance. Despite this, there is a lack of knowledge on this concern. The main objective of this work was to conduct the first systematic review of the diversity of gastrointestinal parasites of SAC throughout the entire native range of distribution and to identify several gaps in knowledge. The PRISMA protocol was performed and a total of 101 documents were summarized. At least 36 parasitic helminths and five Eimeria spp. were registered. This work highlights the need for a greater number of works to know with more certainty the parasitic fauna of camelids in the past and present, in order to achieve predictions that allow proper management of camelids for their future conservation. Furthermore, concerted research efforts are needed to understand the biology, epidemiology, diagnosis and distribution of the parasitosis of SAC along the entire distribution range to guide conservation decisions.


Introduction
The South American camelids (SAC) (Artiodactyla, Camelidae) are a key component of the Andean biocultural heritage (Vilá and Arzamendia, 2020) and have occupied a central role in the development of Andean societies, both for ancient hunter-gatherers and for more recent pastoralists and farmers. SAC were the most important factor in Andean economies and social and ritual life throughout time. SAC include two wild species, the guanaco (Lama guanicoe) and the vicuña (Vicugna vicugna); and two domestic species, the llama (Lama glama) and the alpaca (Vicugna pacos) (Wheeler et al., 2006;Yacobaccio, 2021). This is an endemic group of ungulates adapted to extreme environments with a wide distributionin in arid and semiarid ecosystems from Argentina, Bolivia, Chile, Ecuador and Peru, mainly from 3000 to 5000 m.a.s.l. (Franklin, 2011). The original distribution of SAC includes the Andean high-altitude grasslands, the Altiplano and the Patagonian arid steppes (Vilá and Arzamendia, 2020). The distribution of guanacos includes a wide diversity of open habitats and temperate forest environments of Peru, Bolivia, Chile and Argentina, including Patagonian steppes. The distribution of vicuñas is limited to Northern Argentina, Chile, Peru and Bolivia, restricted to high-altitude Puna environments, above 3400 m.a. s.l. (Vilá, 2012). In pre-Hispanic times, llamas inhabit the Andean regions of Peru, Bolivia, Argentina and Chile and the alpacas were restricted to high and humid environments from the Puna of Peru, Bolivia and Chile (Yacobaccio, 2021). Under the dominion of the Incas (1470-1532), the llama distribution reached the southern Colombia and central Chile. There is no evidence of the presence of alpacas in pre-Columbian sites from Argentina (Olivera and Grant, 2009) and Ecuador (Miller and Gill, 1990) being introduced in these regions later.
Today, husbandry of SAC is an important socioeconomic activity for the Andean populations of South America. Recently, the breeding of domestic camelids also began to have great interest in other parts of the world. Numerous publications have been reported the relevance of parasites of SAC. Endoparasitosis are one of the most common diseases of SAC and have great economic and health relevance. Host-specific parasites and generalistic parasites shared with domestic ruminants such as sheep and goats are well known and have been widely described in the literature (e.g. Navone and Merino 1989;Leguia, 1991;Beldomenico et al., 2003;Aguirre and Cafrune, 2007;Arias-Pacheco et al., 2021). It is known that camelids are parasitized by gastrointestinal nematodes, trematodes and cestodes, and by coccidians, among other parasites. Many of them can cause serious diseases (Fowler, 2010) and can be transmitted to humans, including hydatidosis, fascioliasis, sarcocystosis and toxoplasmosis. The knowledgement of the diversity, spread, and evolution of parasites of SAC play a very important role in the understanding of the behavioral ecology, health, and camelids conservation. Despite this, there is a lack of knowledge about a global vision of gastrointestinal parasite diversity throughout the entire distribution range. The main objective of this work was to conduct the first systematic review of the diversity of gastrointestinal parasites of SAC throughout the native range of distribution and to identify several gaps in knowledge.

Materials and methods
The research was conducted using the systematic approach of the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) protocol guidelines (Shamseer et al., 2015).

Selection criteria
The literature used in this review included publications reporting on gastrointestinal parasites of SAC. The following list gives the criteria used in the selection of publications.
The inclusion criteria were: • Scientific peer-reviewed, scientific papers, conference proceedings and theses (PhD and MSc Thesis and Final Degree Projects) were included. • Literature published in English and Spanish-written in order to include research with local, regional and global impact. • Gastrointestinal parasite analysis of SAC in the natural range of distribution in order to conduct the first review in the subject and to identify gaps in knowledge.
The exclusion criteria were: • Research papers conducted in SAC from sites outside the natural range of distribution. • Research papers on topics other than gastrointestinal parasites of SAC.       The study was focused on gastrointestinal helminths and Eimeria spp., hereafter "parasites". The literature research was carried out on internet through the Google Scholar platform (https://scholar.google. com), the PubMed platform (https://pubmed.ncbi.nlm.nih.gov), and the SciELO platform (https://scielo.org/es/). The following keywords were used for the research: "endoparasites", "gastrointestinal", "intestinal", "parasites", "helminths", "camelids", "South American Camelids", "SAC", "endoparásitos", "parásitos", "intestinales", gastrointestinales", "helmintos", "camélidos", "camélidos sudamericanos", "CSA", "guanaco", "Lama", "Vicugna", "guanicoe", "pacos", "glama", "llama", "alpaca", "vicuña", "Eimeria", "Coccidia". The search rule used in English was (endoparasites OR gastrointestinal OR intestinal) AND (parasites OR helminths OR Eimeria OR coccidia) AND (camelids OR South American camelids OR SAC OR guanaco OR vicuña OR llama OR alpaca OR Lama OR Vicugna) AND (guanicoe OR glama OR vicugna OR pacos). The search rule used in Spanish was (endoparásitos OR parásitos OR helmintos OR Eimeria) AND (intestinales OR gastrointestinales) AND (camélidos OR camélidos sudamericanos OR CSA OR guanaco OR vicuña OR llama OR alpaca OR Lama OR Vicugna) AND (guanicoe OR glama OR vicugna OR pacos). The search was conducted in titles, abstracts and keywords in the above-cited databases, following the selection criteria. The snowball effect in the reference lists was used to increase the scope of the search. The initial search process generated 3960 academic papers from Google Scholar, and additional 285 papers from PubMed and 18 papers from SciELO. The publication retrieval from Google Scholar was scaled down to 237 after removing all parasite papers that did not represent the objective of this review. A flowchart of the PRISMA phases of the search is presented in Fig. 1.

Screening
After the initial search and paper retrieval, 540 academic papers were collected. After removing duplicate information, 482 publications remained. Subsequently, the generated papers were screened by applying the inclusion and exclusion criteria. A total of 98 academic papers were included for quality assessment.

Eligibility
The studies identified after applying the inclusion and exclusion criteria underwent further evaluation to ensure the quality of the research articles. The theses that contained only information published in scientific journals were eliminated. In total, 3 theses were excluded.

Included papers
A total of 95 publications were included in this review. From all reviewed documents, were extracted data regarding geographic location (country and region), number of samples evaluated, number of positive samples, taxa and prevalence of parasites reported, remarks (type of sample, animal characteristics, study remarks) and type of publication, being the data extraction performed by one author with verification by another, as the PRISMA protocol suggest (Shamseer et al., 2015).

Results
The present review includes documents from the period between 1963 and 2022. The information was retrieved from 95 publications and 6 more citations were added (there was no access to the original work), which makes a final number of 101 publications. A total of 74 scientific researchs, 27 theses (PhD and MSc Thesis and Final Degree Projects), four abstracts of scientific meetings and one FAO project were recopiled. The name of parasites was included exactly as reported in the retrieved publications.
The documents summarized belong to five countries (Argentina, Bolivia, Chile, Peru and Ecuador), with the alpaca being the most studied species of SAC, (49.5% of the total documents), followed by the guanaco (23.8%) and finally the llama and vicuña (both 18.8%). The geographical location of the documents summarized is shown in Fig. 2. The map was elaborated with the Google Earth platform.
The reports of parasites of alpacas are summarized in     Table 4. Most of the recopiled documents belong to Argentina (83.33%), while documents from Chile and Peru represent both 8.33%. The data collected throught the entire native range of SAC distribution displayed that the highest species richness of gastrointestinal parasites are found in southern Peru, western Bolivia and central Patagonia. It is important to highlight that this data was elaborated from the information available to date. The parasitic richness found in SAC compiled from the information extracted is represented in Fig. 3.
The gastrointestinal parasites of each of the four SAC species compiled are summarized in Table 5. At least 36 parasitic helminths were registered. Twenty two genera of the Phylum Nematoda have been reported among the four species of SAC. Seventeen genera belong to the Order Strongylida (including 28 taxa identified to the species level), one genus belong to the Order Ascaridida, one genus belong to the Order Oxyurida, one genus belong to the order Rhabditida and two genus belong to the Order Enoplida. Three genera of the Phylum Platyhelminthes were also reported. One of them belongs to Cestoda (with two identified species) and one species belong to Trematoda. Respects to Eimeria spp. (Apicomplexa), five species have been identified. The prevalence of the reported parasitic infestations in many cases was 100% (Tables 1-4). This review displays that there is no one species more prevalent than another, but rather that the prevalence varies in each of the studies.

Discussion
The present work is the first scientific review that provides detailed information about gastrointestinal parasite diversity of SAC throughout the entire native distribution range, encompassing a large number of documents. The records summarized here comprise documents dating from 1963 to 2022, with an increase in the last 10 years, whenever a wide production of scientific publications and graduate and postgraduate theses were produced. This point can be explained by the growing interest in recent years for SAC conservation and, in the other hand, for the economic interest on SAC around the world. The recopilated documents are focused mainly in gastrointestinal parasites studies from fecal samples or from necropsied animals, by microscopic techniques mostly. This implies that in many occasions it is not possible to identify the species. Molecular studies on camelid parasites are scarce. Although 101 works were recopilated, results highlight that a large number of the documents summarized are not published in indexed journals and are not easily accessible to a wider audience.
The highest species richness of gastrointestinal parasites was found in southern Peru, western Bolivia and central Patagonia. This agrees with the regions with the highest population of SAC and with the regions where more studies have been carried out. The important population of Peru explain that this country produced a great number of the available knowledge. However, it is mainly focused on alpaca. Numerous studies considered that latitude is one of the main factors correlated to parasite diversity and richness. Parasite diversity is expected to decrease in high latitude areas as result of lack of intermediate hosts or high mortality rates due to harsh conditions in winter (Krasnov et al., 2004;Lindenfors et al., 2007;Bordes et al., 2010;Poulin and Leung, 2011). The data on parasitic richness of SAC summarized in this paper so far do not allow us to observe a decrease pattern in their distribution throughout their extensive distribution. However, the parasite diversity display in this review should be taken with caution as it is subject to the number and type of samples analyzed in each region. So far, all parasite genera appear to be represented throughout the distribution range.
Most wild and domestic ungulate species have few host-specific parasites, which make up less than half of the total number of nematode parasite species found in a given host; and mostly have generalist parasites (Walker and Morgan, 2014). Across vast areas, SAC coexist with domestic herbivores such as sheep, goat and cattle. Furthermore, domestic SAC coexist with human populations. This proximity facilitates the exchange of parasites between domestic and wild animals and humans. Walker and Morgan (2014) found that domestic camelids (llamas and alpacas) have a high liability index (the degree to which a host species is vulnerable to infection with generalist parasites), with a value of 0.77. This index is designed to range from − 1 (entirely host-specific parasites) to 1 (entirely parasites shared with the other group). This result displays that llamas and alpacas have mostly generalist species. In the present study, 22 genera of nematodes were reported, with at least 33 species. Of all of them, only five are known as SAC-specific nematodes: Trichuris tenuis, Graphinema aucheniae, Camelostrongylus mentulatus, Nematodirus lamae, and Lamanema chavezi. Most of the registered parasites in this review are generalist parasites, and are shared with domestic ungulates and wildlife species, such as Ostertagia spp., Haemonchus contortus, Trichostrongylus spp., Cooperia spp., and Oesophagostomum. From a sanitary point of view, it would be important to know if host-specific parasites dominate the communities of their hosts and generalist parasites tend to occur at lower abundances, or vice versa (Zaffaroni et al., 2000). In this review, is clear that there is not enough data to compare the abundance of different nematode species within a host. Further studies of the contribution of shared parasite species to total parasite burden rather than only species richness would be a step toward understanding the impact that generalist parasites have on SAC. In the other hand, several studies have looked at nematodes of wild ungulates in relation to domestic species. In the present review, domestic SAC displayed to have the same genera of parasites than wild SAC.
SAC have also been described as hosts for parasites of zoonotic importance such as Fasciola hepatica. This trematode was found in wild and domestic camelids, from the north of its distribution to the north of Patagonia. It was generally assumed that entry of F. hepatica to America coincided with the first arrival of the Europeans and their associated livestock in the late 15th century. Throughout the 500 years since its introduction, the parasite gained new definitive hosts among native species. This trematode is now widespread in livestock and can be mapped across the whole South America and certain regions of North America. Nonetheless in Argentina, eggs of F. hepatica have been observed in deer and camelid coprolites dating back to 2300 years B.P.,   prior to the arrival of the European cattle in the 15th century (Beltrame et al., 2020;Tietze et al., 2021). This shows that the presence of Fasciola in camelids is not only due to its transmission by European cattle.
Cestodes found in SACs are ruminant-related anoplocephalid of the genus Moniezia, identified in the four camelids species in a wide variety of environments with records that go from the north of its distribution reaching as far as northern Patagonia. Parasites of Moniezia expansa were identify in all SACs species, while Moniezia benedeni were identify in vicuñas, alpacas and guanacos. In the case of llamas, findings of cestodes were scarce, and in general it was only possible to identify the genus. Recently, Moniezia eggs were also found in coprolites from the middle to late-Holocene from the Argentinian Puna, evidencing the presence of this genus in SAC prior the European cattle arrival (Tietze et al., 2021).
There are five common species of Eimeria in SAC: E. lamae, E. alpacae, E. punoensis, E. macusaniensis and E. ivitaensis (Dubey, 2018). All Eimeria spp. were recorded in wild and domestic camelids throughout its distribution range. The most prevalent Eimeria found in guanacos was E. macusaniensis, but in general the most prevalent in SAC was E. punoensis while the least prevalent was E. ivitaensis (Marin et al., 2009;Rodríguez et al., 2012;Cafrune et al., 2014;Moreno et al., 2015). Of the five Eimeria species registered in SAC, E. macusaniensis is considered the most pathogenic, clinical symptoms can develop even before oocysts are registered in the feces. The host specificity along with the characteristic morphology of its oocyst makes it an effective indicator when identifying the host in coprological studies (Dubey, 2018). The presence of E. macusaniensis is reported even in ancient samples from Argentina, Chile and Peru (Fugassa et al., 2008;Beltrame et al., 2010;Taglioretti et al., 2015;de Souza et al., 2018;Le Bailly et al., 2020;Tietze et al., 2021). When studying the interactions between wildlife, livestock, and their parasites, it will be important to understand the historical context and patterns of contact and relatedness between the host species. A useful tool for this focus is the paleoparasitology. Paleoparasitological studies on SAC have shown the presence of diverse parasitic species in ancient times, which demonstrate the presence of some of them in prehistoric times, before the arrival of the European fauna, and others in more recent archaeological levels. Within the archaeological records were found Dictyocaulus sp., Fasciola hepatica, Lamanema chavezi, Moniezia sp., Nematodirus spathiger, Strongyloides sp., Trichuris sp. (e.g. Taglioretti et al., 2017;Petrigh et al., 2021;Tietze et al., 2021). If we are to make predictions of changes in host-parasite interactions due to, for example, climate or land use change, or to introduction of exotic species, it is necessary to have an exhaustive knowledge of the parasitic diversity of SAC throughout the time and throughout their entire distribution. Environmental changes can modify the epidemiological pattern of parasitic diseases, with impacts on the economy, public health, and/or wildlife conservation (Rhyan and Spraker, 2010). This work highlights the need for a greater number of works to know with more certainty the parasitic fauna of SAC in the past and present, in order to achieve predictions that allow proper management of camelids for their future conservation. Furthermore, concerted research efforts are needed to understand the biology, epidemiology, diagnosis and distribution of the parasitosis of SAC along the entire distribution range to guide conservation decisions.

Conclusions
In summary, this review presents the first compendium of studies of gastrointestinal parasites of SAC throughout the native range of distribution. This serves as a baseline for future studies focused on elucidating the role that parasites play on SAC and further epidemiological research. Clearly, a better understanding of the extent and impact of parasites on SAC, at both the individual and population levels, is needed. This shortfall in knowledge is concerning for SAC conservation.

Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.