Parasite problems in ratite facilities can cause general ill thrift, reduction in growth, poor reproductive results and death. Effective screening prior to introduction into a production unit is essential in the prevention and control of the common ratite parasites. Management procedures in reducing parasitic populations include external feather examinations, complete physical examinations, complete blood counts, direct faecal examinations and faecal floatation examinations.
Arthropods
Ticks are common parasites of the ostrich in its native African environment, and include the following genera/species: Amblyomma spp., Haemaphysalis punctata, Hyalomma spp., Rhipicephalus turanicus and Argus spp. Ticks have been implicated in transmission of viral diseases, and heavy infestations cause ill thrift, slow growth and low egg production. Treatment is best achieved with 5% carbaryl dust at fourteen-day intervals. Pterolichus bicaudatus (ostrich quill mite) and Struthiolipeurus struthionus (ostrich louse) may cause pruritis and/or excessive preening and feather loss. Infestation with these external parasites causes stress and predisposes birds to secondary infections and gastrointestinal disorders (e.g. impactions). Treatment for mites is accomplished with ivermectin, and lice are treated in a similar manner to tick infestations.
Miscellaneous arthropod infestations – e.g. Struthiobosca struthionis in ostriches, Struthiodiperus rheae in rheas, and Culicoides spp. and Simulium spp. in emus – cause blood loss, irritation and stress, and transmit other parasites. Pyrethrin sprays may help to prevent extreme exposure to many of the flying arthropod parasites.
Helminths
Helminth parasites found in ratites include the following: Baylisascaris spp., Libyostrongylus douglassi, Paraonchocerca struthionus, Struthiofilaria megalocephala, Ascaridia orthocerca, Deletrocephalus dimidiatus, Deletrocephalus casarpintoi, Dicheilonema rheae, Paradeletrocephalus minor and Chandlerella quiscali. Baylisascaris spp. have been identified in ostriches and emus (7, 14). The definitive hosts for this parasite are skunks and raccoons, which shed the eggs in faecal material; the eggs can remain infective in the soil for several years. Birds suffering from Baylisascaris spp. infections show ataxia, muscle weakness, recumbency and death, due to visceral larval migration into the brain and spinal cord. Diagnosis is made at necropsy by observation of the parasite in brain or spinal cord tissue sections. Baylisascaris spp. cause a zoonotic parasitic disease and can provoke severe physical damage through visceral larval migration if eggs are ingested. Reduction of definitive host populations around a facility and proper feed storage will help to reduce exposure to this dangerous parasite.
A helminth parasite which affects young emus in a similar manner is Chandlerella quiscali. This parasite is transmitted by Culicoides midges, and visceral larval migration occurs before the birds reach one year of age. Generalized neurological signs accompany Chandlerella spp. infestation, and diagnosis is made at necropsy. Libyostrongylus douglassi (wireworm) is a proventricular parasite which is extremely deadly to young ostrich chicks. Prevention of this parasite from infesting a ratite facility is very important. The life cycle is direct, and pasture rotation is recommended as a control measure. Fenbendazole, levamisole and ivermectin may be effective in the control of this deadly parasite.
The other helminth parasites listed should be treated as mentioned for L. douglassi. Prevention of parasite exposure is the primary management measure recommended in all ratite operations. Once a parasite has become established on a facility, diligent testing and treatment – especially in young birds – will limit economic losses and bird mortality.
Protozoa
The blood protozoa Leucocytozoon struthionis and Plasmodium spp. have been identified in ostriches (7), and are transmitted by flying arthropod vectors. These parasites do not generally cause significant clinical illness, and treatment is usually more problematic than the infestation. The intestinal protozoa Balantidium struthionis, Cryptosporidium spp., Histomonas meleagridis, Hexamita spp., Giardia spp. and Trichomonas spp. cause gastrointestinal problems which result in wasting, anorexia, diarrhoea and death for all ratite species, especially rheas. Direct faecal and intestinal content examinations are essential in diagnosing these parasitic diseases (7). Appropriate treatment with anti-protozoal drugs will reduce losses in an outbreak; but proper husbandry practices will limit incidence, thus reducing labour and other expenses.
Tapeworms and flukes
Houttuynia struthionis (ratite tapeworm) primarily affects younger birds. Ostriches and rheas seem to be the most common ratite species affected, and the recommended treatment is fenbendazole. The adult ratite fluke (Philophthalmus gralli) is found outside the nictitating membrane in affected birds. The intermediate host of the fluke is a freshwater snail, and ratites acquire the parasite through ingestion of freshwater crustaceans or other solid objects. It is recommended that ratite exposure to standing water be restricted, thus reducing the risk of intermediate host exposure.