CASE NOTES
Eimeria macusaniensis causing death in adult alpacas
Kylie Greentree, Hunter LLS, Maitland and Anne Jordan, Elizabeth Macarthur Agricultural Institute
Posted Flock & Herd March 2025
INTRODUCTION
Coccidia are protozoan parasites that can affect a wide range of species, but the impact varies significantly depending on the species, age, health status and environmental conditions. In general, young animals are especially susceptible due to their immature immune systems. Four species of Eimeria are known to infect alpacas in Australia (E macusaniensis (Emac), E lamae, E alpacae and E punoensis). Emac and E lamae are considered to be the most pathogenic (Lenghaus et al. 2004). Common clinical signs of coccidiosis include diarrhoea (+/- blood), weight loss, poor growth, dehydration, lethargy, abdominal discomfort or sometimes sudden death.
CASE REPORT
Six female alpacas were rescued from a property at Blaxland Ridge on 21 July 2024 and brought onto a property in the Lower Hunter. All alpacas were given a quarantine drench (Q-drench) on arrival and a clostridial vaccination. One alpaca died soon after arrival. The alpacas were in poor body condition and had diarrhoea. A private veterinarian was initially involved with this disease investigation. Over two months, the alpacas did not improve or respond to any medication that was provided and three other alpacas died. Throughout the initial diagnostic tests that were done by the private veterinarian, the alpacas had moderate strongyle eggs (larval typing was not done), moderate coccidia counts, one had a PCV of nine and one was tested for Johne' s disease and was negative on ELISA. These alpacas had been drenched with a variety of anthelmintics (Q-drench and Zolvix Plus on different occasions) and given a very low dose of Baycox, two doses four days apart (3mg/kg on initial dose and 4mg/kg on second dose).
In late September, the LLS District Veterinarian was contacted to euthanise the two remaining unwell alpacas, perform a post-mortem and attempt to diagnose what has been the cause of disease with these alpacas. One alpaca was dead on arrival and the other was euthanised.
Figure 1. Opaque, thickened, congested omentum
Alpaca 1 (died overnight). It was in body condition score (BCS) 1 with fat necrosis around the heart, petechial haemorrhages on the epicardium and aspiration into the lungs. The omentum was not transparent but was pale pink and thickened (1.5 times normal). Stomach Compartment-1 (C1) and Compartment-2 (C2) had no abnormalities detected and Compartment-3 (C3) had thickened and submucosal haemorrhage of the torus pyloricus. There was no obvious thickening of the ileocaecal valve or mesenteric lymph nodes in that area and no gross pathology suggestive of Johne's Disease.
Alpaca 2 (euthanised) was in BCS 2. Blood was noticed in the ventral and cranial lung lobes, either from inhalation after the captive bolt or possible pneumonia. Thoracic fluid was 4-5 times normal in volume, and peritoneal fluid was straw-coloured with strings of fibrin and was two times normal in volume. There was increased thickening of the jejunal folds, with no noticeable change in the ileum. The large intestine did not have any signs of blood or thickening.
Post-mortem assessment of both alpacas was vague, with a thickening of the jejunum in alpaca 2 indicating chronic enteritis. Both alpacas had reasonably formed faeces at time of post-mortem, even though they had diarrhoea for two months prior. Multiple fresh and fixed samples were taken from both alpacas and samples were submitted to the Elizabeth Macarthur Agricultural Institute (EMAI) (M24-15243).
Histopathological examination indicated a florid coccidial enteritis evident in both animals, with little normal small intestinal tissue remaining in affected sections. The large size, pyriform shape and thick wall of developing oocysts was consistent with Emac. The infection didn' t appear to be causing significant haemorrhage or necrosis, however assuming a more widespread distribution in the small intestine, it may have caused significant small intestinal dysfunction, such as malabsorption, which could have led to ill-thrift and poor condition. Coccidial infection in alpacas has also been reported to predispose to significant secondary opportunistic bacterial infection, although that wasn' t observed in the examined sections.
Figure 2. Demonstrating an expanded mucosa, replaced by coccidia (black arrows) and active lymphoid tissue (yellow arrow)
Figure 3. Showing thick-walled pyriform oocytes that are the characteristic shape and size of Emac oocytes (black arrow). Microgamonts (green arrow) and macrogamonts (blue arrow) were also present (developing stages of coccidia).
A faecal egg count was performed on both alpacas and Emac was observed in moderate numbers in both alpaca samples. The salmonella culture was negative on both animals.
Figure 4. The above images (B&C) show thick-walled pyriform oocytes that are the characteristic shape and size of Emac oocytes
A faecal examination using the Cornell-Wisconsin method identified large (up to 110µm by 84µm) pyriform-shaped Emac oocytes that exhibit a thick brown wall with a micropyle and micropyle cap (see * in image B). Emac shed these large heavy oocytes in low numbers and intermittently, which means that multiple faecal examinations should be conducted, and faecal examination should be done using a sensitive centrifugal flotation technique with high density sucrose solution (specific gravity of approximately 1.3), with the Cornell-Wisconsin method preferred (Egan et al. 2022). Interestingly, Eimeria species in camelids are morphologically so different in size and shape that species can be identified without the need of sporulation.
DISCUSSION
Emac is highly pathogenic to alpacas of all ages in Australia, resulting in severe damage to the intestinal epithelia and predisposing infected animals to necrotising enteritis, malabsorption, loss of condition, increase susceptibility to bacterial and viral infections and death. Infection is transmitted through contaminated feed, water or the environment where oocysts are present. Emac infections can be seen in alpacas from three weeks to 18 years old (Dubey 2018). Emac has a long prepatent period (33-42 days), so animals can develop disease or even die, prior to detection of oocytes in the faeces. Sporulation of the oocytes (eggs) of Emac will take 13-21 days (depending on temperature) and direct exposure to sunlight will kill unsporulated eggs. Sporulated eggs can survive in the environment for years. Emac damages the crypt epithelium and inhibits epithelial regeneration, consequently exposing the intestine to secondary bacterial or viral invasion (Egan et al. 2022).
The prevalence of Emac has been reported to be significantly lower in adults than in animals under one year of age (Jarvinen 1999). However, 5/6 of the animals in this case were over one year of age. It is unknown if the alpacas in this case came to the rescue property with Emac or picked it up on arrival, but they arrived stressed due to transportation, change of ownership, an unknown property with other alpacas in view (no contact) and in poor body condition with diarrhoea, a moderate internal parasite burden and a coccidia infestation picked up on in-house faecal egg count. Several case reports have diagnosed clinical coccidiosis and death in adult alpacas after the stress of being transported to a new farm (Dubey 2018).
The diagnosis of coccidiosis is usually based on clinical signs and the detection of oocytes in faecal floatation but the absence of coccidial oocytes can be because of an incomplete prepatent period or the use of an insensitive faecal floatation technique (Chigerwe et al. 2007). Gross lesions are most common in the ileum, although any region of the small intestine, caecum and colon may be affected. Mucosal thickening, congestion, plaques and severe haemorrhagic enteritis may be seen in primary lesions. Secondary bacterial infection can lead to necrotic enteritis but sometimes the bowel may appear grossly normal, even with severe infection (Dubey 2018). Coccidiosis must be considered as a differential diagnosis in adult camelids with inappetence, weight loss, possible diarrhoea and sudden death.
ACKNOWLEDGEMENTS
Thanks to Jim Kerr for his collaboration in the field.
REFERENCES
- Chigerwe M, Middleton JR & Kreeger JM (2007) Atypical Coccidiosis in South American Camelids Journal of Veterinary Diagnostic Investigation 19(1):122-125 Atypical Coccidiosis in South American Camelids - Munashe Chigerwe, John R Middleton, Fred Williams, Jeff W Tyler, John M Kreeger, 2007 (sagepub.com)
- Dubey JP (2018) A Review of Coccidiosis in South American Camelids Parasitology research 117:1999-2013 www.pubmed.ncbi.nlm.gov
- Egan R, Avula J & Krystolovich M (2022) Eimeria macusaniensis (E-Mac) intestinal coccidiosis causing acute fatal neurologic disease in an alpaca AHL Newsletter 2022 26(3):10 Eimeria macusaniensis (E-Mac) intestinal coccidiosis causing acute fatal neurologic disease in an alpaca | Animal Health Laboratory (uoguelph.ca)
- Jarvinen JA (1999) Prevalence of Eimeria macusaniensis (Apicomplexa: Eimeriidae) in Midwestern Lama sp. Journal of parasitology 85(2):373-376 Prevalence of Eimeria macusaniensis (Apicomplexa: Eimeriidae) in Midwestern Lama spp. on JSTOR
- Lenghaus C, O' Callaghan MG & Rogers C (2004) Coccidiosis and Sudden Death in an adult alpaca (Lama pacos) Australian Veterinary Journal 82: 711-712 www.onlinelibrary.wiley.com