Nutritional. Herd A. Herd B ... elements, and between trace elements and other nutrients. .... only distantly related to amphibian species previously reported with ...
Table 2. Vitamin E and selenium levels of clinically normal cows in selected beef herds in Ontario Reference herdsa Mean (range) Nutritional component Serum vitamin E
(pg/mL) Vitamin E/cholesterol (ratio) Blood selenium
(p.g/mL)
Herd A (n = 10)
Herd B (n = 10)
Guelph area (n = 10) Mean (range)
Northern Ontario (n = 10) Mean (range)
Western Ontario (n = 10) Mean (range)
AHL range of adequate levels Mean (range)
3.17 (2.49-4.11) 2.59 (1.20-5.21) 0.18 (0.16-0.21)
2.19 (1.90-3.92) 2.26 (1.58-3.03) 0.18 (0.16-0.21)
4.49 (3.13-4.62) 3.11 (2.42-4.68) 0.07 (0.04-0.09)
5.3 (2.98-5.17) 3.61 (2.61-4.55) 0.12
2.73 (2.18-3.90) 2.49 (1.65-3.92) 0.14 (0.05-0.17)
3.0-6.0
(0.09-0.17)
2.5-6.0 0.17-1.20
AHL - Animal Health Laboratories aReference herds were supplemented with selenium in the salt (20 mg/kg salt, for 3 mo)
effects of multiple deficiency problems have received little attention. It is likely that most of the trace mineral deficiency problems experienced by cattle in Ontario are of a subclinical nature. An increase in weaning weight and weight gain in yearlings through trace mineral supplementation has been recorded (3). Improvement in reproductive performance has also been observed with adequate trace mineral supplementation. Recent research has demonstrated that Cu, Zn, Mn, and Se are required for optimum functioning of the immune system in cattle. How much of these trace elements is required to optimize immune function is not known. Some evidence suggests that more Se is required to optimize immune function than is required to prevent white muscle disease, retained placentas, and other problems commonly associated with Se deficiency (4). Producers who have upgraded the trace mineral status of their herds through provision of appropriate supplement have observed improvements in the general health, growth, and reproductive performance of their animals. This is not surprising when one considers that all the animals tested by us were deficient in at least 2 elements, and some in as many as 4. Trace element nutrition of livestock is extremely complicated. Many interactions occur among the trace elements, and between trace elements and other nutrients. These interactions can be very complex and many are
X
not well understood. All trace elements are toxic if fed in excessive amounts. Testing of feed, blood, or tissue levels of trace elements may be warranted from time to time.
Acknowledgment This study was funded in part by the Ontario Cattlemen's Association.
References 1. Young LG, Jenkins KJ, Edmeads DM. Selenium content of feedstuffs grown in Ontario. Can J Anim Sci 1977;57:793-799. 2. Puls R. Mineral Levels in Animal Health. 2nd ed. Clearbrook, British Columbia: Sherpa International, 1994. 3. Marston T. Trace mineral supplementation in beef cattle. Compend Contin Educ Pract Vet 1999;21:S21-S28. 4. Swecker WS, Eversole DE, Thatcher CD, Blodgett DJ, Schurig GG, Meldrum JB. Influence of supplemental selenium on humoral immune responses in weaned beef calves. Am J Vet Res 1989;50: 1760-1763.
Brent Hoff, DVM, DVSc, DipTox, Nick Schrier, MSc, Animal Health Laboratory; Herman Boermans, DVM PhD, Department of Biomedical Sciences, Ontario Veterinary College; Harold Faulkner, PhD, Abdullahi Hussein, Analytical Services Unit, Laboratory Services Division, University of Guelph, Guelph, Ontario.
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British Columbia/Colombie-Britannique Cutaneous chytridiomycosis in dwarf aquatic frogs (Hymenochirus boettgeri) originating from southeast Asia and in a western toad (Bufo boreas) from northeastern British Columbia ten dwarf aquatic frogs (Hymenochirus boettgeri)
were procured from a wholesaler in Florida, USA, in September 1998 by the Vancouver Aquarium Marine Science Centre in Vancouver, British Columbia. Shortly after initial receipt and introduction of the stock, 3 frogs died but were not presented for diagnostic evaluation; because they had died soon after their arrival, the Can Vet J Volume 42, May 2001
Aquarium presumptively attributed the cause of death to physiologic stress associated with transit and acclimation. The remaining 7 frogs were housed in a glass aquarium with a silica sand substrate, a corner charcoal filter, and a few aquatic plants consisting of grasses and floating frogbit or duckweed. The animals were maintained on a diet of artemia and thawed blood worms, and the tank water was exchanged once a week. There was no history of clinical disease and the animals had repeatedly exhibited amplexus. During the 2nd week of May 1999, all 7 remaining frogs died suddenly with no apparent clinical signs; 3 were presented to the Animal Health Centre, Abbotsford, British Columbia for diagnostic evaluation. 385
The frogs were presented intact and fixed in formalin. There were no apparent gross internal or external lesions, except variably extensive cutaneous opacity associated with excess mucus secretion. Microscopically, throughout the ventrum and, to a much lesser extent, the dorsum of the torso, there were variably extensive regions of orthokeratotic hyperkeratosis that were intermittently overlaid by small aggregates of predominantly extracellular bacilli. Interspersed within the hyperkeratotic and, occasionally, hyperplastic epithelium were numerous, discrete fungal organisms, identified as zoosporangia, that contained multiple, 2- to 3-pm, round to oval, multinucleated basophilic thalli. A 2nd shipment of frogs was obtained from the same source in September 1999; within 2 mo of arrival and over the course of 3 to 4 d, all 12 animals succumbed; 8, fixed in formalin, and 4, fresh, were presented for microscopic examination and necropsy, respectively. In the 2nd cohort, there were multifocal to coalescing, raised, smooth, and, occasionally, tufted foci on the skin of the ventrolateral and medial aspects of the coelomic cavity and hind limbs. Microscopic examination revealed intraepidermal organisms identified as chytrid thalli similar to those observed in the original submission, with multifocal, secondary infection by Saprolegnia spp. and scattered, superficial aggregates of extracellular bacilli. In both instances, the lesions and the light microscopic morphology of the fungal organisms were compatible with cutaneous chytridiomycosis caused by a fungus in the phylum Chydridiomycota. Chytridiomycosis is an emerging disease associated with epizootics in wild and captive frog populations. This organism was initially recognized as a pathogen of rainforest frogs in Australia in 1993 and has subsequently been associated with massive die-offs of wild frogs in Panama and elsewhere, through to 1999 (1); more recently, it has been reported in captive poison dart frogs (Dendrobates spp.) and White's tree frogs (Litoria caerulea) maintained at the National Zoological Park in Washington, District of Columbia (2). Historically, this fungus was isolated from plants and invertebrate animals, with no recognized infections of vertebrates. As the skin of frogs is integral for respiration and maintaining acid-base balance, the cause of death of these animals has been postulated to involve impaired gas exchange through affected skin. Although the organism may be isolated by culture, its specialized medium requirements make microscopic examination the most reliable means of diagnosis. This case is unusual in that the dwarf aquatic frog is only distantly related to amphibian species previously reported with the disease and is entirely aquatic. As this frog collection was maintained separately from other stock and fed frozen insect larvae, the animals were likely subclinically infected at the time of acquisition, with mortalities incurred secondary to some other, yet undefined, process. Attempts to ascertain if these frogs were captive-bred in the United States or captured and imported from Africa, and to obtain material for fungal isolation and speciation, are underway. In August 2000, a wild western toad (Bufo boreas) was presented from the northeastern Peace River district 386
of British Columbia with a history of generalized malaise and a prominent cutaneous ulcer in the mid-dorsal region. Microscopic examination disclosed florid chytrid fungal organisms with lesions compatible with those of the African dwarf frogs. This case is believed to record the most northern limit of this organism to date and significantly expands the geographic distribution of chytrids in wild amphibia worldwide. This fungus is considered an important emerging pathogen of wild and captive frog species. Finding it reinforces the need for appropriate quarantine and diagnostic evaluation of recently acquired animals and, apparently, moribund wild frogs.
References 1. Daszak P, Berger L, Cunningham AA, Hyatt AD, Green DE, Speare R. Emerging infectious diseases and amphibian population declines. Emerg Inf Dis 1999:735-748. 2. Pessier AP, Nichols DK, Longcore JE, Fuller MS. Cutaneous chytridiomycosis in poison dart frogs (Dendrobates spp.) and White's tree frogs (Litoria caerulea). J Vet Diagn Invest 1999; 11:194-199.
Stephen Raverty, Animal Health Centre, British Columbia Ministry ofAgriculture and Food, 1767 Angus Campbell Road, Abbotsford, British Columbia V3G 2M3; Tracy Reynolds, Vancouver Aquarium Marine Science Centre, 845 Avison Way, Vancouver, British Columbia V6B 3X8.
Causes of death in captive Vancouver Island marmots (Marmota vancouverensis) including presumptive pulmonary mycoplasmosis V ancouver Island marmots (Marmota vancouverenV*sis), one of 14 species of the genus Marmota, are indigenous to a confined geographical range in southcentral Vancouver Island, British Columbia; they are currently considered one of the most endangered terrestrial mammals in North America (1). Over the course of the last decade, the population of these marmots has declined precipitously. In efforts to enhance public awareness about the plight of these animals, further resolve their natural history, and attempt captive propagation, 16 animals were introduced over the span of approximately 1 y to the
Calgary Zoological Society. The 1st group, consisting of 4 marmots, was introduced in early September 1998. An adult female and a young-of-the-year male succumbed 3 and 10 d postarrival, respectively. The female presented with a profound intestinal cestodiasis (possibly Diandrya composita), necrotizing hepatitis, and bronchopneumonia; whereas, the male was diagnosed with a perforated cecal ulcer and attendant peritonitis, ascribed to a clostridial typhlitis. A 2nd group, consisting of 5 adults was introduced in July 1999; no mortalities were reported. A 3rd group, composed of a single adult female with 6 weaned siblings, arrived in early August 1999; 2 juvenile animals succumbed: one, 17 d after arrival, with a perforated duodenal ulcer and peritonitis; Can Vet J Volume 42, May 2001
