Department of Veterinary Pathology

CASE REPORT RETINAL DYSPLASIA AND INTERNAL HYDROCEPHALUS IN A SHORTHORN CALF H. W. LEaoLD, J. H. L. MT.s AND K. HUSTON* Introduction Ocular anomalies, while reported in most species, have been described only rarely in cattle until recent years (8, 10, 12, 17, 19, 24). Incompletely albino white Hereford cattle had heterochromia irides, tapetum fibrosum hypoplasia, and coloboma of the nontapetal fundus, inherited as an autosomal dominant (8, 11, 12, 15). Several reports of bovine ocular anomalies have recorded abnormalities of other body tissues, especially the heart and central nervous system (14, 16). A study of 681 calves with congenital malformation of the central nervous system and eyes revealed a signifi- cantly higher maternal age for these anomalies (10). A recent review discusses the nature, cause, and effect of bovine congenital defects (17). Bovine hydrocephalus is a frequently en- countered congenital defect but associated FIGuRE 1. Right ocular fundus of 2-day-old ocular lesions are rarely described (16). This female Shorthorn calf. Note leukocoria due to paper records multiple ocular anomalies and retinal detachment. hydrocephalus in a calf from a Shorthorn herd in Saskatchewan. of both eyes was conically detached from the optic disc to the ora ciliaris retinae (Figure History 1). Cornea, anterior chamber, iris, and lens In February 1970, a Saskatchewan breeder were grossly and microscopically normal. The of purebred Shorthorn cattle submitted for detached retinas were folded posterior to the necropsy a two-day-old white female calf. The lens (Figure 2) and, in addition, contained calf, unable to rise, had remained in lateral numerous rosettes (Figure 3). The retinal recumbency since birth. The previous year, folds and rosettes from inside out consisted of one red female calf, blind and unable to rise external limiting membrane, rods and cones, after birth, was destroyed by the owner. and outer nuclear layer. Only a few ganglion cells were visible (Figures 2 and 3). The Description of Defect retinas were entirely dysplastic. The right eye The calf had bilateral microphthalmia; the only had a persistent pupillary membrane. The right eye was 18 by 20 mm by 15 mm; the intraorbital part of the optic nerves measured left eye, 20 by 22 mm by 18 mm. The retina 1.5 mm in diameter, and the intracranial parts were cystic. The optic chiasma and optic tracts also were hypoplastic. Microscopic ex- *Department of Veterinary Pathology (Leipold amination of cross sections of the optic nerves and Mills), Western College ofVeterinary Medicine, at various levels revealed fewer than normal University of Saskatchewan, Saskatoon, Saskatch- nerve bundles but no increase in fibrous septa ewan and the Department of Pathology, Kansas Agricultural Experiment Station, Manhattan, Kan- nor cellular infiltration. sas (Huston). Dr. Leipold's present address is the Associated with the ocular defects was a Department of Pathology, College of Veterinary marked internal hydrocephalus (Figure 4). Medicine, Kansas State University, Manhattan, The lateral ventricles, third ventricle, Sylvian Kansas 66506. aqueduct, and fourth ventricle were dilated. 34 CAN. VET. JOUR., VOl. 15, no. 2, February, 1974 FIGURE 2. Photomicrograph of retinal dyspla- FIGURE 3. Photomicrograph of dysplastic retina. sia. Note folds of retina and rosettes formation. Note formation of rosettes, H & E. X120. H & E. X50. The right lateral ventricle was enlarged con- siderably more than the left. Histological ex- amination of brain sections revealed spongi- ness of subependymal areas. In addition to hydrocephalus, scoliosis to the right of the thoracolumbar spinal column was present. Other organs were grossly and microscopically normal. Breeding History The breeding herd consisted of 35 cows, some registered but most grade, and two unrelated registered bulls. One bull, the principal FIGURE 4. Internal hydrocephalus of Shorthorn herd sire, was unrelated to the 27 females calf affected with retinal dysp asia. with which he was pasture-mated in 1969 and 1970. They produced normal calves. The other bull (G in Figure 5), a roan, was roans (I-2, 10, 11; II-2, 8; III-1, 7; IV-2, 3; pasture mated only with eight registered V-3, 4, 6, 8) and two whites (IV-6, V-7). paternal half sisters in 1969 and again in 1970 (Figure 5). One defective red female was Discussion born in 1969 and one defective white female The pathogenesis of internal hydrocephalus in 1970. In 1970 three cows (III- 2, 3, and 9) in cattle is poorly understood. Many workers failed to evidence signs of pregnancy after six attribute it to recessive genetic factors (2, 4, months with C, and, when subsequently mated 6, 7, 9, 11, 18, 24); others, to incompletely with the other bull, produced calves. All ani- penetrant dominant factors (16, 18). For this mals in the genealogy were red except 13 case, detailed epizootological analysis at the 35 CANADIAN VETERINARY JOURNAL A BI C D1 t)SE U S U 1 2 14 15 16 7 8 19 10 1 12 13 11X 23 4 5 6 7 8 9 i FIGURE 5. Genealogy of retinal dysplasia and internal hydrocephalus in a Shorthorn herd. Key: 0 nonnal female * abnormal female El normal male * abnormal male A non-conception farm revealed no obvious pathogenic agent; exclusively or which they alone transmitted. the remaining evidence contained in the Breed- Among these are hereditarily transmitted agents ing History and Figure 5 may be interpreted and responses. The simplest two hereditary in several ways. agents are a recessive gene or an "incom- First, we must account for the matings in- pletely penetrant" dominant gene. Forms of volving cows III-2, 3 and 9. The low preg- hydrocephalus include not only that which nancy rate in 1970 (5/8) may be an alternate results in perinatal deaths of animals later consequence of the agent which caused hydro- necropsied and found to have hydrocephalus cephalus or simply a coincidental event. It but also that in seemingly normal animals. The would be quite unusual (P < .05) for all genetic term, "incomplete penetrance" is used three infertilities to occur as a coincidental to account for seemingly normal but gen- event in o.Ke year if a common causative agent etically hydrocephalic animals that escaped were present in both years. However if the detection because their brains were not ex- infertility were part of the hydrocephalus syn- amined. drome, that infertility occurrence would not Optional explanations involving an incom- be quite so unusual (P < .05). pletely penetrant dominant gene include as The next hypothesis is that hydocephalus sources of the gene: G, F, or the ancestors of and infertility, from the same or diferent animals II-8, 9, and, if infertility is included, causes, should have appeared with the same II-3, 4, and 10 (Figure 5). Ignoring infertil- frequency in both sire mating groups but ity, all three sources require about 25% pene- occurred only among the mates of G by trance, but G is a favored source because that chance. Such a hypothesis might account for requires fewer unusual sampling events in suc- a nutritional disease or an infectious agent to cessive generations. Next, infertility might be which all females were exposed uniformly. The included as part of the hydrocephalus syn- probability of finding all the hydrocephalic drome, perhaps because the infertility was calves and all the infertile matings concen- thought to have resulted from abortion or re- trated in one group under any of the above sorption of a hydrocephalic fetus during late options is less than the usually accepted 5% gestation. That circumstance requires a pene- level. Hence hypothesis involving unequal oc- trance larger than 1/2 and only G seems a rea- currence in the two groups are favored. Such sonable source of the gene. If the incidence hypothesis might include etiologic agents to of that form of hereditary hydrocephalus which G, his mates, or both were exposed should be as high as 1/1000 calves, a gene 36 HYDROCEPHALUS with high mutation rate of 5 X 10A would be system (14). Retinal dysplasia and internal indicated. hydrocephalus were found in grade Shorthorn The recessive gene interpretation may be calves in Kansas (16). Retinal dysplasia, based on similar assumptions, including or ex- microphthalmia, atrophy, acute and chronic cluding the infertility, as for the dominant neuritis, cataract, and cerebellar hypoplasia gene. Ignoring infertility, a maximum likeli- were caused by the virus of bovine virus hood estimate of the segregation frequency diarrhea-mucosal disease (5). (17) can be based on the two full-sib families Retinal dysplasia combined with hydranen- descended from III-7 and -8. In the latter cephaly in lambs was produced with attenu- case, the estimate can be based on families ated blue tongue virus, a live-virus vaccine from III-2, 3, 7, 8, and 9. Both estimates are nonpathogenic in adult sheep (23). In Sealy- 0; the value expected under recessive in- ham terriers, Bedlington terriers, and Labrador heritance, 0.25. retrievers, retinal dysplasia was caused by The descendents of bull G also may be con- homozygosity of a single autosomal recessive sidered to form an eight-member 3/4 sib fam- gene (1, 3, 21). Whereas Sealyham and Bed- ily, either by choosing one member of each lington terriers had congenital defects re- full sib family randomly or by order of birth, stricted to the eye, the Labrador retrievers or perhaps by using the average of each full had (in five of 14 puppies) dilation of the sib family. In the last case, the segregation heart. Among the five were valvular defects frequency estimate, including infertility, would and one internal hydrocephalus (3). In man, be about 0.19 compared with 0.125 expected retinal dysplasia may be characterized by with recessive inheritance.

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