Identification of an eimeriid parasite infection in camelids from Saudi Arabia: morphology and molecular studiesABSTRACT
Coccidiosis, an intestinal infection caused by protozoan parasites of the genus Eimeria, is a significant health concern in camelids, leading to economic losses in milk and meat production. Little is known about camelid coccidian parasites, with most relying on the prevalence of infection. This study aimed to describe and genetically characterize a camelid’s Eimeria species reported from the Dromedary camel. The taxonomic position of the recovered species was inferred using an analysis of sequences from the nuclear gene 18S rRNA and the mitochondrial gene COI with related taxa. A total of 80 fecal samples from Camelus dromedarius in the old camel market in Riyadh, Saudi Arabia, were collected between December 2023 to February 2024. Before these samples were sporulated in a 2.5% potassium dichromate solution, they were examined for the presence of Eimeria oocysts using the standard floatation technique. The rate of parasitic infections was ascertained. Eimerian oocysts were morphologically described and molecularly characterized using the recommended protocols. Of the 80 examined fecal samples, 18 (22.5%) were positive for Eimeria species. The identified parasite species, Eimeria sp., exhibited high morphometric similarity to Eimeria alpacae, which had a typical ellipsoidal oocyst shape with the presence of micropyle and the absence of oocyst polar granules and residual body. Moreover, sporocysts are elongated in shape and characterized by a distinct stieda body and a residuum within the sporocysts. DNA sequences generated from the 18S rRNA and COI gene regions showed high identity to sequences obtained from oocysts of Eimeria species of the family Columbidae. Phylogenetic analyses using neighbor-joining and maximum likelihood using both sequences from 18S rRNA and COI data consistently grouped the sequences obtained from Eimeria sp. of camel origin, reported in the present study, with DNA sequences in GenBank of domestic pigeon origin. This study highlighted the necessity of describing camel intestinal eimerian parasites using molecular methods rather than traditional morphology-based approaches to gain a better knowledge of their taxonomic status. Moreover, the presence of this eimerian species is considered the first record in Saudi Arabia. Future research studies are recommended to assess the impact of Eimeria infections on camel productivity and health, as well as investigate potential cross-species transmission between camels and other hosts, such as domestic pigeons.
Keywords:
Eimeria spp.; Camelus dromedarius; 18S rRNA, Cytochrome c Oxidase subunit 1; Saudi Arabia
RESUMO
A coccidiose, uma infecção intestinal causada por parasitas protozoários do gênero Eimeria, é um problema de saúde significativo em camelídeos, levando a perdas econômicas na produção de leite e carne. Pouco se sabe sobre os parasitas coccídicos dos camelídeos, com a maioria baseando-se na prevalência da infecção. Este estudo teve como objetivo descrever e caracterizar geneticamente uma espécie de Eimeria de camelídeos relatada no camelo dromedário. A posição taxonômica das espécies recuperadas foi inferida usando uma análise de sequências do gene nuclear 18S rRNA e do gene mitocondrial COI com taxas relacionadas. Um total de 80 amostras fecais de Camelus dromedarius no antigo mercado de camelos em Riyadh, Arábia Saudita, foram coletadas entre dezembro de 2023 e fevereiro de 2024. Antes de essas amostras serem esporuladas em uma solução de dicromato de potássio a 2,5%, elas foram examinadas quanto à presença de oocistos de Eimeria usando a técnica padrão de flotação. A taxa de infecções parasitárias foi determinada. Os oocistos de Eimeria foram descritos morfologicamente e caracterizados molecularmente usando os protocolos recomendados. Das 80 amostras fecais examinadas, 18 (22,5%) foram positivas para espécies de Eimeria. A espécie parasitária identificada, Eimeria sp., apresentou alta similaridade morfométrica com Eimeria alpacae, que tinha uma forma oocística elipsoidal típica com a presença de micrópilo e ausência de grânulos polares oocísticos e corpo residual. Além disso, os esporocistos têm forma alongada e são caracterizados por um corpo stieda distinto e um resíduo dentro dos esporocistos. As sequências de DNA geradas a partir das regiões dos genes 18S rRNA e COI mostraram alta identidade com as sequências obtidas a partir de oocistos de espécies de Eimeria da família Columbidae. Análises filogenéticas usando neighbor-joining e máxima verossimilhança usando ambas as sequências de 18S rRNA e dados COI agruparam consistentemente as sequências obtidas de Eimeria sp. de origem camelo, relatadas no presente estudo, com sequências de DNA no GenBank de origem pombo doméstico. Este estudo destacou a necessidade de descrever os parasitas eiméricos intestinais de camelos usando métodos moleculares, em vez de abordagens tradicionais baseadas na morfologia, para obter um melhor conhecimento de seu status taxonômico. Além disso, a presença dessa espécie eimérica é considerada o primeiro registro na Arábia Saudita. Recomenda-se que estudos futuros avaliem o impacto das infecções por Eimeria na produtividade e saúde dos camelos, bem como investiguem a potencial transmissão entre espécies entre camelos e outros hospedeiros, como pombos domésticos.
Palavras-chave:
Eimeria spp.; Camelus dromedarius; 18S rRNA, subunidade 1 da citocromo c oxidase; Arábia Saudita
INTRODUCTION
In Saudi Arabia, the demand for animal protein has been increasing significantly along with the continuous increase in the human population (Al-Shaebi et al., 2024). The one-humped camel, Camelus dromedaries, is the most common species within the Camelidae family. Camels have been an essential animal in inhospitable regions, where they are used for transportation, agricultural labor, food, milk, and skin production (Burger et al., 2019). Camels may play a role in the epidemiology of some parasitic zoonotic diseases, especially due to the lack of enough sanitation interferences (Sazmand et al., 2019). Gastrointestinal parasites, including protozoans and helminths, are major contributors to reduced camel productivity (Bouasla et al., 2023).
Eimeria species are intracellular protozoans that colonize the gastrointestinal tract and cause coccidiosis. This infection can lead to high morbidity and mortality, particularly in severe cases (Rewatkar et al., 2009). Several Eimeria species are widely distributed and exhibit high prevalence rates among camelids (Radfar and Gowhari, 2013). Camels with severe Eimeria infections exhibit gastroenteritis symptoms, including weight loss, lethargy, and watery or bloody diarrhea (Dubey, 2018). Coccidiosis may predispose camels to secondary infections, including those caused by viruses, bacteria, fungi, or other parasites (Hastutiek et al., 2022).
Eimeria species are host-specific parasites with a monoxenous life cycle, comprising two intestinal phases (asexual and sexual replication) and an environmental sporogony phase (sporulation) (Bangoura and Bardsley, 2020). Eimeria species are transmitted via the fecal-oral route, with both symptomatic and carrier animals shedding non-sporulated oocysts in their feces (Sazmand et al., 2012). Under optimal environmental conditions, oocysts sporulate within 2-7 days and remain infective for several months (Malek and Kuraa, 2018). Variation in the prevalence of Eimeria parasites is influenced by factors such as environmental conditions, animal physiology and health, farming practices, sickness, and stress (Al-Shaebi et al., 2024). In Saudi Arabia, few studies are available about the prevalence of Eimeria species among camelids (Kawasmeh and Elbihari, 1983; Kasim et al., 1985; Hussein et al., 1987; Al-Megrin, 2015; Metwally et al., 2020; Al-Shaebi et al., 2024).
Traditionally, Eimeria species are identified through characteristics such as the pre-patent period, oocyst morphology and morphometry, and site of development in the host (Meireles et al., 2004). Due to the challenges of identifying Eimeria species based on oocyst morphology, molecular characterization is crucial for accurate species-level identification (Hastutiek et al., 2022). Recent progress demonstrated that some PCR-based methods utilizing genetic markers in nuclear ribosomal DNA provide rapid and powerful complementary diagnostic tools (Morris and Gasser, 2006; Al-Shaebi et al., 2024). A species-specific PCR diagnostic assay was developed based on variable sequence regions, and specific primers were constructed for the differentiation of Eimeria species (Su et al., 2003; Al-Shaebi et al., 2024). The specific diagnosis of different Eimeria species is central to the prevention, surveillance, and control of coccidiosis (Khaier et al., 2015; Al-Shaebi et al., 2024). This study aims to identify specific Eimeria species in the dromedary camels (Camelus dromedarius), understand genetic diversity, and develop diagnostic tools.
MATERIALS AND METHODS
Fecal samples were collected randomly from 80 dromedary camels (Camelus dromedarius) of both sexes at different ages from December 2023 to February 2024, admitted to the old camel market in Riyadh (Saudi Arabia). Each sample was placed into screw-capped plastic containers and labeled with epidemiological data, then transported within 3-4 hr to the Laboratory of Parasitology, College of Science, King Saud University, Saudi Arabia.
Each fecal sample was examined by the floatation method using saturated saline solution (Sheather’s solution, specific gravity = 1.28), as reported by Soulsby (1982). A part of each fecal sample (3g) was weighed and mixed with 42ml of saturated sucrose solution. The mixture was subjected to centrifugal sedimentation (1500 rpm for 3 min) at room temperature (RT). The samples were examined using a light microscope (Olympus Corporation, Tokyo, Japan). To identify the species, oocysts were collected and allowed to sporulate in a 2.5% (w/v) aqueous potassium dichromate solution in Petri dishes in the air at room temperature for a week, according to Menezes and Iopes (1995). After sporulation, the contents of the Petri dishes were centrifuged at 1500 rpm for 3 min, and the supernatant fluid was decanted. The sediment was suspended in 1× phosphate-buffered saline (PBS), and the centrifugation was repeated several times until the supernatant fluid became clear. The morphological and morphometric features of oocysts were investigated under a Leica DM 2500 microscope (NIS ELEMENTS software, version 3.8) using an oil immersion lens. Based on 50 oocysts, measurements were made using ImageJ 1.53e software (Wayne Rasband and contributors, National Institute of Health, USA).
A commercial QIAamp DNA Stool Mini Kit (Qiagen, Valencia, CA) was used to extract the genomic DNA from the Eimeria oocysts following the company protocol. PCR was performed under specific conditions that targeted the partial nuclear ribosomal small subunit RNA (18S rRNA) and mitochondrial cytochrome c oxidase-1 (COI) gene regions. Amplification was carried out utilizing the genus-specific primers, as follows: for the 18S rRNA gene region was 5′-TAC CCA ATG AAA ACA GTT T-3′ and 5′-CAG GAG AAG CCA AGG TAG G-3′ (Orlandi et al., 2003), and for the COI gene region was 5′-GGT TCA GGT GTT GGT TGG AC-3′ and 5′-AAT CCA ATA ACC GCA CCA AG-3′ (Ogedengbe et al., 2011). A MultigeneTM thermocycler (Labnet International, Inc., NJ, USA) was used to control cycling conditions: initial denaturation (94°C for 2min), denaturation (94°C for 50s), annealing (50°C [18S rRNA] and 52°C [COI] for 30s), and extension at 72°C for 30s in 35 cycles. PCR products were subjected to electrophoresis on a 1.5% (w/v) agarose gel (Sigma-Aldrich, USA) and stained with SYBR Safe DNA gel dye (Thermo Fischer Scientific, Canada). The DNA fragment size was confirmed using a 100bp ladder (Fermentas, Lithuania). The PCR products were examined and visualized using a gel documentation system (Image Analyzer, UK). Sequencing was performed using the Sanger dideoxy method available from Macrogen® (Seoul, South Korea) using the same PCR primers mentioned above. The obtained sequences were compared with those available in GenBank using the BLASTn tool. Consensus sequences were aligned along with publicly available species sequences using CLUSTAL-X software (Thompson et al., 1997). Phylogenetic trees were constructed using the maximum likelihood (ML) and Neighbour Joining (NJ) methods as implemented in MEGA X software (Tamura et al., 2021). Data were bootstrap-resampled 1000 times to estimate relative branch support.
Data analysis was performed using SPSS (version 18, SPSS Inc., Chicago). Measurements were presented in micrometers (µm) as the mean, with the range in parentheses.
RESULTS
A fecal examination of all samples showed that 22.5% (18 out of 80 camels) were found positive for Eimeria species. One Eimeria species was identified from camels according to morphological and morphometric parameters of oocysts (Table 1 and Figure 1) as Eimeria sp.
Morphological features for the isolated Eimeria sp. oocysts infecting camels. (A) Non-sporulated oocyst. (B and C) Sporulated oocysts. (Note: OL, outer layer; IL, inner layer; S, sporont; MP, micropyle; SPC, sporocyst; SPZ, sporozoite; RF, refractile body; RBS, residuum of sporocyst).
Description (Table 1 and Fig. 1). Non-sporulated oocysts are ellipsoidal, measuring 18.19-22.48 (19.77) in length and 16.24-19.28 (16.90) in width (Figure 1A). The oocyst wall is double-layered, with the outer one being thicker and the inner one being membranous (Figure 1A). The micropyle is present (Figure 1A). The sporont (zygote) is cylindrical, measuring 11.77-13.92 (12.91)×11.26-13.87 (12.46) (Figure 1A). Sporulation took 7 days at 27°C to occur.
Sporulated oocysts are ellipsoidal, measuring 21.77-25.69 (23.68) in length and 18.72-22.30 (19.91) in width, with the presence of a micropyle (Figure 1B). Oocystic polar granule and oocyst residuum are absent (Figure 1B). Each oocyst was tetrasporozoic (Figure 1B). Sporocysts are elongated, measuring 10.85-12.33 (11.57) in length and 6.24-7.03 (6.67) in width. They have a single-layered wall with a distinct stieda body (Figure 1B). Sporocyst residuum exists between the two sporozoites (Figure 1B). Each sporocyst is dizoic. Sporozoites are elongated, lying longitudinally head to tail in the sporocysts, 8.13-9.96 (9.38)×2.01-3.08 (2.54), with one broad end and the other narrower but pointed (Figure 1B). Each sporozoite has one refractile body at the wider end (Figure 1B).
The amplification of both 18S rRNA (~613 bp) and COI (~ 650 bp) gene regions, using the DNA extracted from the oocysts recovered from the camel feces, was successful, and sequences were obtained. Two sequences were obtained from each of the 18S rRNA and COI gene regions and deposited in GenBank, and were given the accession numbers PQ637269-PQ637270 for the 18S rRNA gene region and PQ666440-PQ666441 for the COI gene region. Sequencing chromatograms of both the 18S rRNA and COI loci produced clear peaks without evidence of mixed sequences. Phylogenetic analyses of the sequences were obtained from the DNA extracted from the oocysts obtained from camel feces. Phylogenetic analyses were based on 518 positions of 18S rRNA region and 645 positions for COI datasets using neighbor-joining (NJ) and Maximum Likelihood (ML) analyses. Both sequences generated from the amplification of the 18S rRNA locus were identical, whereas those resulting from the amplification of the COI locus were unidentical and showed differences in 9 positions.
The phylogenetic tree resulting from the 18S rRNA sequence data showed one major clade that grouped eimerian species from the Columbidae, including domestic pigeons (Columba livia domestica) from different parts of the world (Figure 2). The two sequences resulting from the PCR product of the 18S rRNA were identical, and they grouped with two sequences, OR739606 and OR742109, which have been reported from a domestic pigeon in Tabriz, Iran, from two separate investigations (Figure 2). The sequence identity between the sequences obtained from the present study and sequences in the same clade, consisting of eimerian parasites from Columbidae, was found to range from 97.2% to 98.7%. Some other sequences that were used in the present analysis and grouped with the two sequences obtained from the present study were not fully described, and they are designated as Eimeria spp.
Analysis of the COI data resulted in a similar topology on both analyses (NJ and ML), grouping the two new sequences from the present study with sequences obtained from eimeriid parasites of Columbidae (Figure 3). They shared a common ancestor with the sequence OQ681029, which was reported from eimerian oocysts from domestic pigeons, to which they showed 99.6% sequence identity. Sequences were also very close to another sequence, OP558169, which was reported from domestic pigeons from Poland, with 98.6% sequence identity. Sequences from eimerian parasites from the partridges and skunks were placed on separate clades (Figure 3). There are only two sequences available in GenBank (OR576777 and MN473487), which are labeled as COI sequences from Eimeria alpacae from China. The sequences were 465 bp and 438 bp long, respectively, and they do not span the full length of the sequences we obtained in the present study. The fragments from both sequences from E. alpacae, which were compared with the sequences obtained from the oocysts of the present study, were 432 bp. In this length, there were 64 and 66 (of OR576777 and MN473487, respectively) differences in the nucleotide positions and the sequences obtained from camel in the present study, bringing up the percentage of sequence identity to 85.2% and 84.7%, respectively. Phylogenetic analysis from the inclusion of the two sequences from E. alpacae has clearly shown that the sequences resulting from our study are distant from those sequences. They clustered separately in one clade (Figure 4).
A consensus phylogenetic tree was inferred by using the Maximum Likelihood (ML) and Neighbor Joining (NJ) methods based on the Tamura-Nei model (Tamura and Nei, 1993) using MEGA software 7 (Kumar et al., 2016). The tree is drawn to scale, with branch lengths measured in the number of substitutions per site. The analysis involved 34 nucleotide sequences of the 18S rRNA region, including relevant sequences available in GenBank, together with Toxoplasma gondii as an outgroup. All positions containing gaps and missing data were eliminated. There was a total of 518 positions in the final dataset. New sequences from Eimeria sp. resulting from the present study are shown in bold and indicated with a filled circle (●). Bootstrap values are given along branches as ML/NJ.
A consensus phylogenetic tree was inferred by using the Maximum Likelihood (ML) and Neighbor Joining (NJ) methods based on the Tamura-Nei model (Tamura and Nei, 1993) using MEGA software 7 (Kumar et al., 2016). The tree is drawn to scale, with branch lengths measured in the number of substitutions per site. The analysis involved 24 nucleotide sequences of the COI region, including relevant sequences available in GenBank, together with Toxoplasma gondii as an outgroup. All positions containing gaps and missing data were eliminated. There was a total of 645 positions in the final dataset. New sequences from Eimeria sp. resulting from the present study are shown in bold and indicated with a filled circle (●). Bootstrap values are given along branches as ML/NJ.
A consensus phylogenetic tree was inferred by using the Maximum Likelihood (ML) and Neighbor Joining (NJ) methods based on the Tamura-Nei model (Tamura and Nei, 1993) using MEGA software 7 (Kumar et al., 2016). The tree is drawn to scale, with branch lengths measured in the number of substitutions per site. The analysis involved 20 nucleotide sequences of the COI region, including relevant sequences available in GenBank, including two sequences from Eimeria alpacae given in solid triangles (▲), together with Toxoplasma gondii as an outgroup. All positions containing gaps and missing data were eliminated. There was a total of 429 positions in the final dataset. New sequences from Eimeria sp. resulting from the present study are shown in bold and indicated with a filled circle (●). Bootstrap values are given along branches as ML/NJ.
DISCUSSION
The oocysts detected in the present study morphologically resemble those reported from Alpacas (Lama pacos), which were identified as Eimeria sp. by Guerrero (1967). However, molecular analyses revealed that the DNA sequences of these oocysts clustered with sequences obtained from Eimeria species infecting Columbidae. Consistent results were obtained from both the 18S rRNA and COI regions. Given that samples were directly collected from camels, the possibility of contamination with pigeon droppings is highly unlikely. Additionally, Eimeria species are generally considered host-specific, although cases of host-switching have been documented, particularly in rodents (Mácová et al., 2018).
One of the main challenges in interpreting these results is the scarcity of molecular data from Eimeria species infecting Camelidae. A recent study by Al-Shaebi et al. (2024) provided 18S rRNA sequences from Eimeria rajasthani; however, these sequences do not align with those obtained in the present study. This suggests that the Eimeria parasites infecting camels may be distinct from known species. While it is possible that Eimeria species of Camelidae do not share a recent common ancestor, further phylogenetic analyses with a broader dataset are required to resolve their evolutionary relationships.
Coccidian intestinal parasite infections have a significant economic impact on camels due to losses associated with enteritis, diarrhea, decreased body weight, and reduced meat yield and quality (Sazmand et al., 2019). However, the epidemiology of coccidian infections in Saudi Arabian camels remains poorly understood. Thus, the goal of this study was to enhance our understanding of Eimeria infections in camelids within the study area by conducting both coprological and molecular investigations. A single Eimeria species was identified infecting dromedary camels sourced from the old camel market in Riyadh, Saudi Arabia.
Comparative studies on Eimeria species in closely related camelid hosts provide valuable insights. Frezzato et al. (2020) identified five Eimeria species infecting alpacas, including E. alpacae, E. lamae, E. punoensis, E. macusaniensis, and E. ivitaensis. The Eimeria species identified in this study is more closely related to E. alpacae, previously described in alpacas, but was found infecting dromedary camels.
The presence of E. alpacae in dromedary camels raises questions about potential cross-transmission. One possible explanation is the environmental contamination of food or water sources with eimerian oocysts from other camelid species, although alpacas are not commonly found in the region. Given that most camels in Saudi Arabia are imported from the Horn of Africa (Tolah et al., 2020), further investigation is needed to determine whether Eimeria species from African camelids contribute to this transmission. While cross-transmission of Eimeria species through contaminated water or feed has been documented in other livestock (Chartier and Paraud, 2012), further studies are required to determine whether E. alpacae can infect multiple camelid hosts and whether oocysts can persist under transport conditions.
Regarding the morphometric features, the presence of a visible micropyle and ellipsoidal form, as well as the measurements of the oocysts (sporulated and non-sporulated), served as the primary distinguishing features for the recovered Eimeria species. Our descriptions of the sporulated Eimeria oocysts were similar to those of Guerrero (1967). However, Schrey et al. (1991) reported the presence of round-ovoid oocysts for E. alpacae with a visible micropyle. Additionally, oocyst shape and micropyle are not mentioned for E. alpacae in studies by Foreyt and Lagerquist (1992), Duszynski et al. (2001), and Añamuro et al. (2024). The sporocyst features are missing in the description of E. alpacae from Lama glama (Foreyt and Lagerquist, 1992) and Vicugna pacos (Añamuro et al., 2024). Moreover, the sporocyst residuum and stieda body were not mentioned in the described species of E. alpacae by Duszynski et al. (2001). According to the presented data by Dubey (2018), the studied Eimeria oocysts differ from those Eimeria species infecting alpacas by (i) the size of sporulated oocysts (vs. 93.6×67.4µm of E. macusaniensis, 88.8×51.8µm of E. ivitaensis, 35.6×24.5 µm of E. lamae, and 19.9×16.4µm of E. punoensis), (ii) the ellipsoidal shape of oocysts (vs. ovoid in E. macusaniensis), (iii) the presence of micropyle (vs. absent in E. ivitaensis), and (iv) the size of sporocysts (vs. 36.3×18.3µm of E. macusaniensis, 35.4×13.1 µm of E. ivitaensis, 15.2×8.5µm of E. lamae, and 9.2×6.1µm of E. punoensis).
The infection rate of the recovered Eimeria species in dromedary camels was 22.5%. Various studies have reported the prevalence of Eimeria infection in camelid populations worldwide. Antony Rodríguez et al. (2012) recorded a 45.6% prevalence of E. alpacae in alpacas examined at the Research and Production Center “CIP - La Raya,” University of the Altiplano of Puno, Peru. Similarly, Wilson Martela et al. (2022) reported E. alpacae infection in Vicugna vicugna in Bolivia, with prevalence’s of 37.8% in Sarcarí and Sausalito (Villazón - Potpsí), 64.3% and 58.8% in Pulario (Yunchara - Tarija), and 30% in Altamachi (Cocapata - Cochabamba). Additionally, Añamuro et al. (2024) studied coccidiosis in alpacas during the peripartum period in Puno, Peru, and found an E. alpacae prevalence of 86%. According to Sazmand et al. (2019), variations in Eimeria prevalence are influenced by multiple factors, including dietary habits, climate, farm management practices, and host health conditions (e.g., illness and stress). However, Foreyt and Lagerquist (1992) reported that E. alpacae is not considered pathogenic, even in young animals.
Our study confirms the presence of an Eimeria species in camelids, supported by morphological and morphometric data. In cases where morphological differentiation is challenging due to similarities in shape and size, molecular analysis has become a valuable tool for accurate identification (Hassum et al., 2007; Mohammed et al., 2024).
Sequences obtained from the present study were obtained from oocysts that were recovered from camel feces. However, they showed a close relationship to sequences obtained from pigeons from different parts of the world. They showed 98.6% and 99.6% identity to sequences from pigeons from Iran (Tabriz) and Poland. There were no similar sequences from eimerian parasites from a camel in GenBank for comparison. The only two sequences from COI related to E. alpacae (OR576777 and MN473487) were shorter than the sequences reported in the present study; furthermore, they shared 85.2% and 84.7% with both sequences from Eimeria sp. of the present study (Cui et al., 2024). Interestingly, the source of the sequence (OR576777) was neither a camel nor a pigeon. It was detected from the Eurasian lynx (Lynx lynx), which is unlikely to be E. alpacae unless there was close contact between alpacas and Eurasian lynx in China. The other sequence (MN473487) was reported from a fecal sample of an alpaca in China. However, the work was not published for further details. It is unclear whether the DNA detected from the fecal sample of the lynx is morphologically related to E. alpacae or not, as there was no morphological description by Cui et al. (2024). Furthermore, the morphology of the oocysts from which the E. alpacae DNA sequence (MN473487) was isolated is unavailable for comparison. The oocysts described in the present study, together with COI sequences, were surely obtained from camels. The oocysts sporulated in 7 days, which indicated that the origin of the oocysts was the camel. The clustering of the sequences from the 18S rRNA and COI loci with sequences from pigeons is interesting and difficult to explain. Morphologically, the oocysts did not look like any of the oocysts reported from domestic pigeons. Recently, oocysts of Eimeria labbaena-like from the Riyadh region measured 20.4×16.4 µm, which is much smaller than what has been reported in the present study. Therefore, it is unlikely that it may have resulted from contamination of oocysts from pigeons. Furthermore, the sequences obtained from oocysts recovered from pigeons and camels in Riyadh are quite distinct. The detection of bird parasites in mammals was reported before by Mirza (1970), who found Isospora sp. oocysts in the feces of 2 of 4 Gazella sp. in Iraq. Also, he suggested that such oocysts belonged to Isospora lacazae of sparrows. Since there was no detailed description for the oocysts, it may well be that the oocysts are related to Gazella sp. in which it was originally detected. Schuster et al. (2017) were able to describe Isopsora orlovi from camels, and they claimed that the transmission of the infection to young mothers may be through milk. Furthermore, they also stated that ingestion of oocysts by adult animals does not lead to patent infection. It is strongly believed that the oocysts detected in the present study are of camel origin since the unsporulated oocysts have been shed and sporulated in 7 days.
CONCLUSION
This study probably provides a further understanding of the eimerian species infecting the dromedary camel. The parasite was obtained from camel feces, and it showed morphological resemblance to Eimeria alpacae from the New World camelid. However, molecular data placed the sequences from both 18S rRNA and COI data with eimerian parasites from pigeons. There was no morphological similarity between the oocysts recovered in the present study and related oocysts from pigeons. Therefore, the eimerian oocysts described in the present study may constitute a new species of Eimeria from camels. Hence, further work is required to investigate the prevalence of this organism in various camel populations throughout the Kingdom and describe it as a new species of Eimeria infecting camels.
ACKNOWLEDGMENTS
This study was supported by Ongoing Research Funding Program (ORF-2025-94), King Saud University, Riyadh, Saudi Arabia.
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