The family Gruidae includes 15 species, 11 of which are considered vulnerable or endangered with extinction in the wild by the IUCN. Captive crane collections represent an invaluable resource for the preservation of genetic resources, sources of cranes for re-introduction or stocking programs, and public education efforts. Thorough preventive medicine programs play an integral role in promoting the health and safety of these unique populations.

At the International Crane Foundation (ICF), preventive medicine is delivered by a team consisting of the veterinarian and veterinary technician, aviculturists, the public education staff and volunteers. By engaging each group and fostering communication among them with regular opportunities to share information, all members become stakeholders in the preventive health program. Each group performs vital daily, weekly and seasonal tasks that contribute to our understanding of individual crane and flock health throughout the year.

Our program focuses on daily visual evaluation of each flock member, provision of high quality nutrition, husbandry that maximizes worker efficiency and bird safety while minimizing disturbance, routine examinations and diagnostic testing for developing young, annual health examinations of flock members after the breeding season, biannual fecal parasite evaluation and annual pen rotation, and pre-transfer/pre-release diagnostic testing protocols as well as quarantine and testing protocols for cranes entering the ICF flock.

Daily observations are made by the aviculture staff both morning and late afternoon, and focus on changes in physical activity, behavior, food consumption or the appearance of other clinical signs of disease¹. Education staff members and volunteers provide opportunistic observations on cranes currently on exhibit throughout the day, and are instructed to notify aviculture staff members if abnormalities are observed. In turn, notification of the education staff is important in the event of an emergency involving a crane on exhibit for assistance with visitor management. Daily contact provides timely detection and response for acute problems such as trauma, orthopedic conditions, beak and feather conditions, entanglements or failures in pen structures (fencing, shade cloth, flight netting, doorways), or the sudden onset of illness. Afternoon checks are made at least one hour prior to closing in order to assure the availability of personnel on grounds to respond in case of emergency.

ICF's nutritional policy is aimed at providing superior nutrition for the health, reproduction and well being of all 15 species of cranes. The use of formulated diets with captive cranes has a long history and has involved collaboration among a variety of aviculturists, researchers and nutritionists. All diets are subjected to palatability/acceptance and quality control testing. Batches of new feed are sampled randomly on arrival prior to storage under refrigeration. Pelleted feed is analyzed for nutrient (crude protein, dry matter and minerals) and mold/yeast content. Feed samples may also be used for other microbiological (e.g., Salmonella) and toxicological (e.g., mycotoxin) screening if the results of food testing warrant. Batches of new feed are then tested for acceptance and palatability by feeding the diet to birds on exhibit for a 2 week period with the exception of endangered species. Once deemed accepted and without clinical effects, the new diet is fed to the entire collection. All batches are labeled to assure proper sequential use of inventory. Products not used within 6 months are disposed of (sooner if not under refrigeration).

Currently, ICF uses commercially prepared feeds from Zeigler Brothers, Inc., Gardners, Pennsylvania, USA; diets from Mazuri, St. Louis, Missouri, USA have also been used. Zeigler diets are preferred for use in whooping cranes that are managed for maximum egg production, as the breeder diet contains higher concentrations of potentially limiting amino acids found in avian eggs. Both diets are adequate for maintenance of crane collections, and are comparable in cost. Zeigler produces a higher protein chick starter diet with limited sulfur-containing amino acids to help reduce the risk of abnormal leg development from rapid growth.

Daily and seasonal husbandry of cranes at ICF minimizes disturbance to these sensitive, territorial birds whenever possible. Pen cleaning, feeding and watering, and small maintenance projects are performed in a regimented fashion each morning, in as few different sites simultaneously as possible. Veterinary examinations are coordinated with aviculture work whenever possible to avoid repeated daily visits. Larger maintenance or construction projects are conducted after the breeding season whenever possible, as territorial behaviors and sensitivity to disturbance wane. Cranes are locked into their indoor enclosures if disturbance is expected to be significant or if severe inclement weather is predicted.

The pens provided at ICF are designed to provide adequate space, minimize injuries and stress (primarily through placement of visual barriers), and limit the build-up of microorganisms and parasites. Indoor enclosures provide a soft substrate, such as sand or wood shavings, and adequate light and ventilation and supplemental heat (for young chicks and tropical species in winter). If cranes are rotated to alternate pens annually and have access to an area of at least 50 m² per crane, outdoor pens do not normally need to be cleaned³. Indoor enclosure bedding is cleaned at one to two day intervals, with complete removal of wet bedding and fecal material. Sand bedding is sifted through a 3mm mesh screen. Diluted bleach or commercial disinfectants are used to clean surfaces in all crane pens after complete removal of bedding material at least annually.

Four distinct protocols for the examination of crane chicks have been developed at ICF based on the conservation status of the species involved and whether the chick is to be hand-reared, costume-reared or reared by adult cranes. Each protocol gradually decreases the frequency of examinations as the chicks reach fledging age, with special attention to neonatal care, physical examination and weight determination, fecal parasite screening, fecal culture for Salmonella, and blood sampling for PCV/TPP determination and sexing. Each protocol allows for direct comparison of age-matched cranes across years and to standardized growth charts across species. The frequency of examinations is important as many hand-reared cranes appear pre-disposed to toe, hock and leg disorders¹, especially in the face of excessive weight gain. Treatments, modifications to feeding regimens, and exercise management are facilitated by increased veterinary-aviculturist contact.

Currently, no prophylactic treatments for parasites are given to chicks at ICF. Treatment is tailored to positive fecal examination results (typically nematode parasites such as Capillaria sp.). Parasitism by coccidia (Eimeria gruis or E. reichenowi) can be common in captive crane collections and may result in significant pathology via extraintestinal dissemination. Concentrations of coccidia in soil are exacerbated by overcrowding in small pens. Control measures usually include pen rotation, regular fecal parasite examination, and age class separation of cranes². The use of the coccidiostat monensin, milled into pelleted feed at 90 g/ton, may also be advisable.

ICF currently does not routinely vaccinate its cranes against West Nile virus (WNV) due to the apparent low viral activity in rural south-central Wisconsin. We have, however, documented seroconversion in 10% of the flock, among 8 species. One clinical case occurred in the past 10 years: a geriatric sandhill crane (Grus canadensis) with WNV encephalitis in 2006⁴. Other zoological institutions have reported morbidity and mortality only in sandhill cranes, a native North American species. Vaccination programs for chicks and adults of many species have been implemented using the Fort Dodge (Iowa, USA) killed equine WNV vaccine. Research suggests the vaccine is safe to use in young sandhill cranes, and promotes greater antibody titers and more limited viral shedding than controls following challenge with WNV. The efficacy of the vaccine under field conditions appears acceptable.

At ICF, whooping cranes are vaccinated against the alphavirus causing eastern equine encephalitis (EEE), due to the species apparent susceptibility. Chicks are routinely vaccinated at approximately 35 days of age, and then given a booster 2–4 weeks later. EEE vaccine is not used routinely in other Gruidae, but may be considered if regional activity increases.

Annual health checks of all flock members are conducted in fall after the breeding season at ICF. The examinations are conducted in a large event requiring numerous volunteers, and are designed to keep disturbance at the facility localized to a single day. The examinations include: physical examination, weight, PCV/TPP determination, and blood smear preparation (or CBC). Serological investigations (inclusion body disease of cranes (IBDC), WNV, etc.) are conducted infrequently. A rotating sample of the flock (10% of the total) have cloacal swabs tested for Salmonella sp. Problems identified at health check are followed up with more thorough work-ups depending on the urgency of the problem(s). Adult whooping cranes are given a booster vaccination against EEE annually.

The ICF parasite control program involves twice yearly fecal examinations of adult flock members performed in coordination with the pen rotation scheme. No prophylactic treatments are done due to low parasite prevalence at ICF. Exams are performed in late winter (February), two months prior to breeding season, and late summer (post breeding). Direct smears and fecal floatations are performed on every bird or pair; fecal sedimentation tests are done on every bird or pairs with significant access to standing water during the summer (i.e., pond) to screen for trematode ova. Cranes with negative fecal examinations are immediately rotated; otherwise all positive fecal results are treated, rechecked 2 weeks after the last treatment, and then rotated if negative. Typical nematode parasites such as Capillaria, ascarids and gapeworms are treated with fenbendazole (100 mg/kg PO) and ivermectin (0.2 mg/kg SQ) twice, two weeks apart.

Pre-transfer/pre-release evaluations are an important part of maintaining health in captive collections worldwide and preventing transmission of potential pathogens to wild crane populations in re-introduction programs. This testing would also be valuable for screening rehabilitated cranes prior to release. Our pre-transfer protocol includes: complete physical examination including weight, CBC/serum chemistry panel, fecal culture for Salmonella, IBDC serology, fecal parasite examinations (ideally two tests two weeks apart), and a microchip transponder check or placement. The physical examination is done within 4 weeks of departure. All birds are also re-evaluated by the aviculture staff when handled for transfer. The additional tests must have been done within 1 month (CBC, chemistry panel, cloacal swab culture, second fecal) to six months (first fecal, IBDC serology) depending on recent history and age.

All incoming birds to ICF are quarantined for a minimum of 30 days to protect the core breeding flock from disease introduction; the length is extended until all diagnostic results are available, all necessary treatments are completed, or if it is considered necessary to monitor for a specific suspected disease (e.g., avian mycobacteriosis). No routine prophylactic treatment is done. ICF expects the institution of origin to conduct pre-shipment testing similar to ICF pre-transfer testing to provide as complete a health history as possible around this important time. Standard quarantine testing includes: complete physical examination at time of arrival, CBC/serum chemistry panel, culture of cloacal swab for aerobic bacteria (to provide baseline data and to screen for Salmonella), IBDC serology, and fecal parasite analysis (three tests two weeks apart). Additional testing may be required in the case of international imports or reception of birds from areas with known endemic diseases of concern for cranes, such as EEE or highly pathogenic avian influenza.

References

1.  Carpenter JW. Gruiformes (cranes, limpkins, rails, gallinules, coots, bustards). In: Zoo and Wild Animal Medicine, 5th edition, Fowler ME, Miller RE, eds. Saunders, Saint Louis, MO. 2003; 171–180.

2.  Olsen GH. Cranes. In: Handbook of Avian Medicine, 2nd ed. Tully TN, Dorrestein GM, Jones AK, eds. Saunders, Philadelphia, PA. 2009; 243–257.

3.  Swengel SR, Carpenter JW. General husbandry. In: Cranes: Their Biology, Husbandry, and Conservation, Ellis DE, Gee GF, Mirande CM, eds. National Biological Service, Washington, D.C., and International Crane Foundation, Baraboo, Wisconsin, USA. 1996; 31–44. Available online: www.pwrc.usgs.gov/resshow/gee/cranbook/cranebook.htm

4.  Hansen CH, Hartup BK, Gonzalez OD, Lyman DE, Steinberg H. West Nile encephalitis in a captive Florida sandhill crane. Proceedings of the North American Crane Workshop 2008;10:115–118.