Naturally acquired immunity to Plasmodium pitheci in Bornean orangutans (Pongo pygmaeus).

Naturally acquired immunity to the different types of malaria in humans occurs in areas of endemic transmission and results in asymptomatic infection of peripheral blood. The current study examined the possibility of naturally acquired immunity in Bornean orangutans, Pongo pygmaeus, exposed to endemic Plasmodium pitheci malaria. A total of 2140 peripheral blood samples were collected between January 2017 and December 2022 from a cohort of 135 orangutans housed at a natural forested Rescue and Rehabilitation Centre in West Kalimantan, Indonesia. Each individual was observed for an average of 4.3 years during the study period. Blood samples were examined by microscopy and polymerase chain reaction for the presence of plasmodial parasites. Infection rates and parasitaemia levels were measured among age groups and all 20 documented clinical malaria cases were reviewed to estimate the incidence of illness and risk ratios among age groups. A case group of all 17 individuals that had experienced clinical malaria and a control group of 34 individuals having an event of >2000 parasites µL−1 blood but with no outward or clinical sign of illness were studied. Immature orangutans had higher-grade and more frequent parasitaemia events, but mature individuals were more likely to suffer from clinical malaria than juveniles. The case orangutans having patent clinical malaria were 256 times more likely to have had no parasitaemia event in the prior year relative to asymptomatic control orangutans. The findings are consistent with rapidly acquired immunity to P. pitheci illness among orangutans that wanes without re-exposure to the pathogen.

USE OF A HUMAN INDIRECT IMMUNOFLUORESCENCE ANTIBODY ASSAY FOR BALAMUTHIA MANDRILLARIS IN A GROUP OF CAPTIVE NORTHWEST BORNEAN ORANGUTANS (PONGO PYGMAEUS PYGMAEUS).

Granulomatous amoebic encephalitis caused by the free-living amoeba Balamuthia mandrillaris is a highly fatal disease that was first isolated from a mandrill (Mandrillus sphinx), and has since been diagnosed in several nonhuman primates including orangutans. Indirect immunofluorescence antibody (IFA) techniques for Balamuthia have been used in the fields of human medicine and epidemiology both for exposure assessment and screening of clinical patients for antemortem diagnosis. Stored serum samples from five captive Northwest Bornean orangutans (Pongo pygmaeus pygmaeus), including one who had died from B. mandrillaris infection, housed at a single facility were screened with a human IFA assay for B. mandrillaris. Only the single, clinically affected individual was seropositive, and the results suggest that the use of the available human B. mandrillaris IFA assay is a novel diagnostic option for detection of Balamuthia antibodies in this species. A validated screening serological test could be used in individuals exhibiting signs consistent with granulomatous amoebic encephalitis to facilitate earlier antemortem diagnosis of Balamuthia infection, which is critical if treatment is to be pursued. This pilot study presents the use of serological detection methods for B. mandrillaris screening in a nonhuman primate. Subsequent use of the B. mandrillaris IFA assay in the larger captive population should be pursued for validation of the test and to provide further information on seroprevalence and evaluation of risk factors for exposure to Balamuthia and subsequent development of disease.

Genetic characterization of nodular worm infections in Asian Apes.

Parasitic nematodes of Oesophagostomum spp., commonly known, as 'nodular worms' are emerging as the most widely distributed and prevalent zoonotic nematodes. Oesophagostomum infections are well documented in African non-human primates; however, the taxonomy, distribution and transmission of Oesophagostomum in Asian non-human primates are not adequately studied. To better understand which Oesophagostomum species infect Asian non-human primates and determine their phylogeny we analysed 55 faecal samples from 50 orangutan and 5 gibbon individuals from Borneo and Sumatra. Both microscopy and molecular results revealed that semi-wild animals had higher Oesophagostomum infection prevalence than free ranging animals. Based on sequence genotyping analysis targeting the Internal transcribed spacer 2 of rDNA, we report for the first time the presence of O. aculeatum in Sumatran apes. Population genetic analysis shows that there is significant genetic differentiation between Bornean and Sumatran O. aculeatum populations. Our results clearly reveal that O. aculeatum in free-ranging animals have a higher genetic variation than those in semi-wild animals, demonstrating that O. aculeatum is circulating naturally in wildlife and zoonotic transmission is possible. Further studies should be conducted to better understand the epidemiology and dynamics of Oesophagostomum transmission between humans, non-human primates and other wild species and livestock in Southeast Asia.

First report of Leishmania infantum infection in the endangered orangutan (Pongo pygmaeus pygmaeus) in Madrid, Spain.

BACKGROUND: Some wild animals have been recognized as potential reservoirs of Leishmania infantum infection (e.g. carnivores, lagomorphs, rodents, etc.). Leishmania infantum was also identified infecting humans and lagomorphs (i.e. hares and rabbits) over the period of 2009-2016, with the latter acting as the main reservoirs involved in the human leishmaniosis outbreak in Madrid. RESULTS: Two cases of clinical leishmaniosis are reported in orangutans (Pongo pygmaeus pygmaeus) housed at two different centres in Madrid. The first is the case of a 36-year-old male orangutan with severe weight loss and apathy. A complete blood count and biochemical profile revealed anaemia, neutropenia, hypoalbuminaemia and elevated transaminases. Hepato-splenomegaly was also observed. Four months later, due to worsening of clinical signs (mainly bilateral epistaxis), blood and bone marrow samples were collected. Amastigotes of L. infantum were detected in macrophages from a bone marrow aspirate and by specific polymerase chain reaction. The second case was a 34-year-old female orangutan with severe weight loss and apathy and no other apparent clinical signs. A complete blood count and biochemical profile revealed anaemia, pancytopenia and hypoalbuminaemia. Splenomegaly and pericardial effusion were also observed. As leishmaniosis was included in the differential diagnosis, both blood and bone marrow samples were collected. Leishmania infantum infection was confirmed by microscopy, molecular diagnosis and serology (immunofluorescence antibody test). Both animals were treated daily with oral miltefosine for 28 days; allopurinol was also given uninterruptedly in Case 2 for at least 6 months. During follow-up, though good clinical recovery was clear, a lack of parasitological cure was confirmed molecularly in both blood and bone marrow samples from the two orangutans. In both habitats, the presence of the sand fly vector identified as Phlebotomus perniciosus was confirmed. CONCLUSIONS: To our knowledge, this is the first report of L. infantum infection in great apes and in the endangered species P. p. pygmaeus. We are presently looking for L. infantum in other non-human primates living in the same peri-urban areas. If detected, we will examine the impacts of this serious disease on these critically endangered species.

Prevalence of Cryptosporidium spp., Enterocytozoon bieneusi, Encephalitozoon spp. and Giardia intestinalis in Wild, Semi-Wild and Captive Orangutans (Pongo abelii and Pongo pygmaeus) on Sumatra and Borneo, Indonesia.

BACKGROUND: Orangutans are critically endangered primarily due to loss and fragmentation of their natural habitat. This could bring them into closer contact with humans and increase the risk of zoonotic pathogen transmission. AIMS: To describe the prevalence and diversity of Cryptosporidium spp., microsporidia and Giardia intestinalis in orangutans at seven sites on Sumatra and Kalimantan, and to evaluate the impact of orangutans' habituation and location on the occurrence of these zoonotic protists. RESULT: The overall prevalence of parasites in 298 examined animals was 11.1%. The most prevalent microsporidia was Encephalitozoon cuniculi genotype II, found in 21 animals (7.0%). Enterocytozoon bieneusi genotype D (n = 5) and novel genotype Pongo 2 were detected only in six individuals (2.0%). To the best of our knowledge, this is the first report of these parasites in orangutans. Eight animals were positive for Cryptosporidium spp. (2.7%), including C. parvum (n = 2) and C. muris (n = 6). Giardia intestinalis assemblage B, subtype MB6, was identified in a single individual. While no significant differences between the different human contact level groups (p = 0.479-0.670) or between the different islands (p = 0.992) were reported in case of E. bieneusi or E. cuniculi, Cryptosporidium spp. was significantly less frequently detected in wild individuals (p < 2×10-16) and was significantly more prevalent in orangutans on Kalimantan than on Sumatra (p < 2×10-16). CONCLUSION: Our results revealed that wild orangutans are significantly less frequently infected by Cryptosporidium spp. than captive and semi-wild animals. In addition, this parasite was more frequently detected at localities on Kalimantan. In contrast, we did not detect any significant difference in the prevalence of microsporidia between the studied groups of animals. The sources and transmission modes of infections were not determined, as this would require repeated sampling of individuals, examination of water sources, and sampling of humans and animals sharing the habitat with orangutans.

Definitive Hosts of Versteria Tapeworms (Cestoda: Taeniidae) Causing Fatal Infection in North America.

We previously reported fatal infection of a captive Bornean orangutan with metacestodes of a novel taeniid tapeworm, Versteria sp. New data implicate mustelids as definitive hosts of these tapeworms in North America. At least 2 parasite genetic lineages circulate in North America, representing separate introductions from Eurasia.

Phylogenetic relationships between pinworms (Nematoda: Enterobiinae) parasitising the critically endangered orang-utan, according to the characterisation of molecular genomic and mitochondrial markers.

Pinworms (Nematoda: Enterobiinae) include 52 species parasitising primates throughout the world. In the present study, we performed the first ever molecular analysis to investigate the phylogenetic position of recently described pinworms parasitising the Sumatran orang-utan. The phylogenetic analysis of mitochondrial CO1 and chromosomal 18S rDNA and ITS1 regions could support the independent status of several Nematoda species. Our molecular data clearly suggest that Enterobius (Colobenterobius) buckleyi and Lemuricola (Protenterobius) pongoi together with Pongobius hugoti form separate clades among other studied species, which significantly supports the hypothesis of recently described new species parasitising the orang-utan (Pongo abelii and Pongo pygmaeus). The phylogenetic tree based on cytochrome oxidase 1 (CO1) gene variability showed possible close relationships between L. (Protenterobius) pongoi and P. hugoti; thus, we can assume that these species could have initially diverged in sympatry from a common ancestor.

Fatal metacestode infection in Bornean orangutan caused by unknown Versteria species.

A captive juvenile Bornean orangutan (Pongo pygmaeus) died from an unknown disseminated parasitic infection. Deep sequencing of DNA from infected tissues, followed by gene-specific PCR and sequencing, revealed a divergent species within the newly proposed genus Versteria (Cestoda: Taeniidae). Versteria may represent a previously unrecognized risk to primate health.

Genetic characterization of Strongyloides spp. from captive, semi-captive and wild Bornean orangutans (Pongo pygmaeus) in Central and East Kalimantan, Borneo, Indonesia.

Orangutans (Pongo spp.), Asia's only great apes, are threatened in their survival due to habitat loss, hunting and infections. Nematodes of the genus Strongyloides may represent a severe cause of death in wild and captive individuals. In order to better understand which Strongyloides species/subspecies infect orangutans under different conditions, larvae were isolated from fecal material collected in Indonesia from 9 captive, 2 semi-captive and 9 wild individuals, 18 captive groups of Bornean orangutans and from 1 human working with wild orangutans. Genotyping was done at the genomic rDNA locus (part of the 18S rRNA gene and internal transcribed spacer 1, ITS1) by sequencing amplicons. Thirty isolates, including the one from the human, could be identified as S. fuelleborni fuelleborni with 18S rRNA gene identities of 98·5-100%, with a corresponding published sequence. The ITS1 sequences could be determined for 17 of these isolates revealing a huge variability and 2 main clusters without obvious pattern with regard to attributes of the hosts. The ITS1 amplicons of 2 isolates were cloned and sequenced, revealing considerable variability indicative of mixed infections. One isolate from a captive individual was identified as S. stercoralis (18S rRNA) and showed 99% identity (ITS1) with S. stercoralis sequences from geographically distinct locations and host species. The findings are significant with regard to the zoonotic nature of these parasites and might contribute to the conservation of remaining orangutan populations.

Parasites found from the feces of Bornean orangutans in Danum Valley, Sabah, Malaysia, with a redescription of Pongobius hugoti and the description of a new species of Pongobius (Nematoda: Oxyuridae).

In order to obtain basic data on parasitic infections of Bornean orangutans, Pongo pygmaeus morio (Owen, 1837), in Danum Valley, Sabah, Malaysia, fecal examinations were conducted. Based on a total of 73 fecal samples from 25 individuals, cysts of Entamoeba coli, Entamoeba spp., and Chilomastix mesnili, cysts and trophozoites of Balantidium coli, and eggs of Trichuris sp. or spp., unknown strongylid(s), Strongyloides fuelleborni, and an unknown oxyurid, plus a rhabditoid larva of Strongyloides sp., were found. Mature and immature worms of Pongobius hugoti Barus et al., 2007 and Pongobius foitovae n. sp. (Oxyuridae: Enterobiinae) were recovered from fecal debris and described. Pongobius foitovae is readily distinguished from P. hugoti by having a much longer esophageal corpus, a longer and distally hooked spicule in males, and a more posteriorly positioned vulva in female. Presence of plural species of non- Enterobius pinworms is a remarkable feature of the orangutan-pinworm relationship, which may reflect speciation process of the orangutans, host switching, and coevolution by pinworms.

Intestinal parasites of endangered orangutans (Pongo pygmaeus) in Central and East Kalimantan, Borneo, Indonesia.

Faecal samples from 163 captive and semi-captive individuals, 61 samples from wild individuals and 38 samples from captive groups of Bornean orangutans (Pongo pygmaeus) in Kalimantan, Indonesia, were collected during one rainy season (November 2005-May 2006) and screened for intestinal parasites using sodium acetate-acetic acid-formalin-concentration (SAFC), sedimentation, flotation, McMaster- and Baermann techniques. We aimed to identify factors influencing infection risk for specific intestinal parasites in wild orangutans and individuals living in captivity. Various genera of Protozoa (including Entamoeba, Endolimax, Iodamoeba, Balantidium, Giardia and Blastocystis), nematodes (such as Strongyloides, Trichuris, Ascaris, Enterobius, Trichostrongylus and hookworms) and one trematode (a dicrocoeliid) were identified. For the first time, the cestode Hymenolepis was detected in orangutans. Highest prevalences were found for Strongyloides (individuals 37%; groups 58%), hookworms (41%; 58%), Balantidium (40%; 61%), Entamoeba coli (29%; 53%) and a trichostrongylid (13%; 32%). In re-introduction centres, infants were at higher risk of infection with Strongyloides than adults. Infection risk for hookworms was significantly higher in wild males compared with females. In groups, the centres themselves had a significant influence on the infection risk for Balantidium. Ranging patterns of wild orangutans, overcrowding in captivity and a shift of age composition in favour of immatures seemed to be the most likely factors leading to these results.

Presence and species identification of the gapeworm Mammomonogamus laryngeus (Railliet, 1899) (Syngamidae: Nematoda) in a semi-wild population of Sumatran orangutan (Pongo abelii) in Indonesia.

One adult syngamid nematode parasite couple was found during routine clinical observation in quarantine at the former Bohorok Rehabilitation Station from sputum of Pongo abelli and determined as Mammomonogamus laryngeus [Railliet, A., 1899. Syngame laryngieu du boeuf. Comptes Rendus Hebdomadaires des Séances et Mémoires de la Société de Biologie 11, 18-21]. This finding confirmed previous record of ova and adult syngamid nematodes, determined by Collet et al. [Collet, J.-Z., Galdikas, B.M.F., Sugarjito, J., Jojosudharmo, S., 1986. A coprological study of parasitism in orangutan (Pongo pygmaeus) in Indonesia. Journal of Medical Primatology 15, 121-129] as Mammomonogamus sp. only, in orangutans kept in the Bohorok Orangutan Rehabilitation Centre (Northern Sumatra, Indonesia) and presented a serious health hazard to rehabilitants in this locality. Morphometrical features and the first description of the parasite from orang-utan were presented and documented. Coprological monitoring of infection in rehabilitants in this area as well as among the wild population of orangutan is necessary.

The impact of ecological conditions on the prevalence of malaria among orangutans.

Contemporary human land use patterns have led to changes in orangutan ecology, such as the loss of habitat. One management response to orangutan habitat loss is to relocate orangutans into regions of intact, protected habitat. Young orangutans are also kept as pets and have at times been a valuable commodity in the illegal pet trade. In response to this situation, government authorities have taken law enforcement action by removing these animals from private hands and attempted to rehabilitate and release these orangutans. In relocating free-ranging orangutans, the animals are typically held isolated or with family members for <48 h and released, but during the course of rehabilitation, orangutans often spend some time in captive and semicaptive group settings. Captive/semicaptive groups have a higher density of orangutans than wild populations, and differ in other ways that may influence susceptibility to infectious disease. In order to determine the impact of these ecological settings on malaria, the prevalence of malaria was compared between 31 captive and semicaptive orangutans in a rehabilitation program at the Sepilok Orangutan Rehabilitation Centre and 43 wild orangutans being moved in a translocation project. The prevalence of malaria parasites, as determined by blood smear and Plasmodium genus-specific nested-polymerase chain reaction, was greater in the captive/semicaptive population (29 of 31) than in the wild population (5 of 43) even when accounting for age bias. This discrepancy is discussed in the context of population changes associated with the management of orangutans in captive/semicaptive setting, in particular a 50-fold increase in orangutan population density. The results provide an example of how an ecological change can influence pathogen prevalence.

Platynosomum fastosum in ex-captive orangutans from Indonesia.

The liver fluke Platynosomum fastosum was identified upon necropsy of three ex-captive orangutans (Pongo pygmaeus) which had been part of a rehabilitation program for reintroduction to the wild. This trematode has not been reported in orangutans previously and is commonly found in cats in Southeast Asia. Cross infection from cats via intermediate hosts, to orangutans kept in captivity as pets, could explain their presence in the latter. Although P. fastosum caused intrahepatic and bile duct damage, death of the hosts could not be attributed solely to the presence of the liver fluke infection.

A coprological study of parasitism in orangutans (Pongo pygmaeus) in Indonesia.

Fecal specimens from 89 orangutans (36 captive, 34 rehabilitant, and 19 wild) at different locations in Indonesia were examined. Strongyloides spp, Balantidium coli, and strongylid nematodes were the most common infestations detected. A syngamid nematode, Mammomonogamus sp, is reported for the first time in orangutans.