Genetic Selection for Resistance to Gastrointestinal Parasitism in Meat Goats and Hair Sheep through a Performance Test with Artificial Infection of Haemonchus contortus.

Internal parasitism has been the leading cause of morbidity and mortality in small ruminants in many areas such as the southcentral USA. Among the different approaches and management practices to cope with internal parasitism, genetic selection for internal parasite resistance is recognized as one with considerable potential long-term impact. A central performance test with artificial infection of Haemonchus contortus for selection of growing meat goats and hair sheep for breeding to increase resistance to internal parasitism and on-farm selection of females was conducted for 3 years. The results varied considerably among breeds of goats and flocks of sheep. Spanish goats and St. Croix sheep maintained relatively low fecal egg count (FEC) each year, whereas for goats categorized as being of high resistance and Dorper sheep FEC decreased with advancing year. Packed call volume (PCV) and total serum immunoglobulin (Ig) levels were not strongly related to FEC. Genetic parameters varied between the two species, which might be related to previous selection pressure exerted for parasite resistance. Heritability of FEC was higher in goats than sheep. The genetic correlation between FEC and IgM and IgG was negative for both species, which suggests possible genetic association. Genetic and phenotypic correlations between ADG and FEC were nonsignificant for both species. In conclusion, different relationships of FEC and PCV between species require careful attention during selection and the lack of relationship between ADG and FEC suggests that selection of growing male meat goats and hair sheep for resistance to internal parasitism will not adversely affect growth performance.

Signatures of selection for resistance to Haemonchus contortus in sheep and goats.

BACKGROUND: Gastrointestinal nematode infection (GNI) is the most important disease affecting the small ruminant industry in U.S. The environmental conditions in the southern United States are ideal for the survival of the most pathogenic gastrointestinal nematode, Haemonchus contortus. Host genetic variation for resistance to H. contortus allows selective breeding for increased resistance of animals. This selection process increases the prevalence of particular alleles in sheep and goats and creates unique genetic patterns in the genome of these species. The aim of this study was to identify loci with divergent allelic frequencies in a candidate gene panel of 100 genes using two different approaches (frequentist and Bayesian) to estimate Fst outliers in three different breeds of sheep and goats exposed to H. contortus. RESULTS: Our results for sheep populations showed SNPs under selection in C3AR1, CSF3, SOCS2, NOS2, STAT5B, TGFB2 and IL2RA genes using frequentist and Bayesian approaches. For goats, SNPs in CD1D, ITGA9, IL12A, IL13RA1, CD86 and TGFB2 genes were under selection. Common signatures of selection in both species were observed in NOS2, TGFB2 and TLR4 genes. Directional selection was present in all SNPs evaluated in the present study. CONCLUSIONS: A total of 13 SNPs within 7 genes of our candidate gene panel related to H. contortus exposure were identified under selection in sheep populations. For goats, 11 SNPs within 7 genes were identified under selection. Results from this study support the hypothesis that resistance to H. contortus is likely to be controlled by many loci. Shared signatures of selection related to mechanisms of immune protection against H. contortus infection in sheep and goats could be useful targets in breeding programs aimed to produce resistant animals with low FEC.

A case of acute posterior multifocal placoid pigment epitheliopathy demonstrating vogt-koyanagi-harada disease-like optical coherence tomography findings in the acute stage.

PURPOSE: We report a case of acute posterior multifocal placoid pigment epitheliopathy (APMPPE), which was difficult to differentiate from posterior pole-type Vogt-Koyanagi-Harada (VKH) disease because the lesions were mainly located in the macula bilaterally. CASE REPORT: A 33-year-old man presented with rapid bilateral loss of vision. Fundoscopy revealed yellow-white subretinal lesions in the posterior pole of both eyes. Optical coherence tomography (OCT) revealed the presence of subretinal fluid with a subretinal septum. After initiation of systemic steroids, OCT revealed that the amount of subretinal fluid decreased immediately. However, vision loss was less responsive to the therapy, and OCT revealed partial reorganization of the inner segment/outer segment (IS/OS) line in the bilateral macular areas after therapy. DISCUSSION: In our case, the location of the macular lesions made it difficult to differentiate APMPPE from VKH disease by fluorescein angiography. OCT images showed VKH disease-like findings of serous retinal detachment with a subretinal septum. The outer nuclear layer disappeared and the IS/OS line in the affected area was disorganized in the acute stage of the disease. In this case, the rapid loss of vision was specific to the onset pattern of APMPPE, and the slow response to therapy was very different from the response typically observed in VKH disease. Thus, careful consideration of the clinical course is important for diagnosing APMPPE.

Choroidal folds in acute-stage vogt-koyanagi-harada disease patients with relatively short axial length.

PURPOSE: To report 2 cases of Vogt-Koyanagi-Harada disease accompanied by remarkable choroidal folds in the acute stage. The early indicator of recurrence in these 2 cases was the identification of choroidal folds by spectral-domain optical coherence tomography (SD-OCT). CASE REPORTS: A 68-year-old woman (Case 1) presented with visual loss in both eyes. Funduscopic examination revealed optic disc swelling and serous retinal detachment in both eyes. SD-OCT revealed remarkable choroidal folds and serous retinal detachment. After the initiation of systemic steroid treatment, choroidal folds disappeared rapidly and the amount of serous retinal detachment reduced remarkably. Choroidal folds observed on SD-OCT were the early indicators of recurrence prior to the emergence of serous retinal detachment. A 62-year-old woman (Case 2) presented with bilateral blurred vision and metamorphopsia. SD-OCT showed remarkable choroidal folds and serous retinal detachment in both eyes. After the initiation of systemic steroid treatment, choroidal folds and serous retinal detachment disappeared. At the time of recurrence, choroidal folds were observed by OCT. DISCUSSION: During monitoring of Vogt-Koyanagi-Harada disease treatment, choroidal folds could be an early sign of recurrence. When choroidal folds are observed and recognized as an early indicator of recurrence, a prompt increase in steroids can improve the patients' prognosis. Finally, both cases presented here had relatively short axial lengths, and we speculate that a shortened axial length may be a cause of choroidal folds in the acute stage of the disease.