Development and validation of a new vision screening test algorithm for public use mobile application- A pilot study

OBJECTIVES

To design and develop a simple vision test algorithm for mobile application and perform a pilot study to determine its validity and reliability as a tool for vision test in the community.

METHODS

A simple visual acuity test algorithm in the form of a single letter E display was designed as the optotype for development of a mobile application. The standardised optotype is presented at random to test visual acuity for corresponding level of 3/60, 6/60, 6/18, and 6/12. The final result is auto-generated based on the classification of the WHO for visual impairment and blindness. The Snellen chart was used as the gold standard to determine its validity while five different users were involved to determine its inter-rater reliability. A pilot study was performed between April till November 2019, in the Universiti Sultan Zainal Abidin Medical Centre (UMC) at Kuala Nerus and Mooris Optometrist Centre at Marang, Terengganu. A total of 279 participants aged four years old and above were involved in this study.

RESULTS

The highest sensitivity was found at the vision level cut-off point of 6/12 with the percentage of 92.7% and 86.8% for the right and left eye, respectively. The specificity was more than 89% for all vision levels in both eyes. The Krippendorff's alpha value for the inter-rater reliability was 0.87 and 0.83.

CONCLUSION

The relatively high level of validity and reliability obtained indicate the feasibility of using the designed optotype to develop a valid and reliable mobile app for vision test. The app can be used to screen vision by nonmedical persons, at anytime and anywhere to help improve public awareness and capability to correctly determine their visual status.

Interpretations of antibody responses to Salmonella enterica serotype enteritidis gm flagellin in poultry flocks are enhanced by a kinetics-based enzyme-linked immunosorbent assay

Many regulatory and diagnostic programs for the detection of Salmonella enterica serotype Enteritidis infection in commercial poultry flocks have relied on rapid Pullorum agglutination tests to screen birds because of the shared antigens of S. enterica Enteritidis and S. enterica Pullorum and Gallinarum; however, the use of the enzyme-linked immunosorbent assay (ELISA) format affords better analytical sensitivity than crude agglutination tests. In this study, we adapted our earlier conventional indirect ELISA, using gm flagellin as the antigen, to a kinetics-based, computer-controlled ELISA (KELA). The KELA was used to screen for flagellin antibody from three commercial flocks: (i) a large flock involved in a U.S. Department of Agriculture trace back from a human S. enterica Enteritidis foodborne outbreak (n = 3,209), (ii) a flock infected with the endemic S. enterica Enteritidis serotype but which also had multiple other Salmonella serotypes (n = 65), and (iii) an S. enterica Pullorum-infected flock (n = 12). The first flock (S. enterica Enteritidis prevalence of 2.45% based on culture) provided a field test of the KELA and allowed the calculation of diagnostic sensitivity (D-Sn) and diagnostic specificity (D-Sp). With a cutoff of 10 (used for screening flocks [i.e., high sensitivity]), the KELA has a D-Sn of 95.2% and a D-Sp of 18.5%; with a cutoff of 140 (used in confirmatory flock testing [i.e., high specificity]), the KELA has a D-Sn of 28.0% and a D-Sp of 99.1%. We found that with a cutoff of 60 (D-Sn = 63.1%; D-Sp = 91.6%), we could eliminate reactions in the KELA caused by other non-S. enterica Enteritidis salmonellae. The KELA was also compared to two commercial rapid Pullorum tests, the Solvay (D-Sn = 94.9%; D-Sp = 55.5%) and the Vineland (D-Sn = 62.0%; D-Sp = 75.3%).

Proximal tibiotarsal infarcts in turkeys

Necrotic lesions in the proximal tibiotarsal bones of turkeys were evaluated by pathologic and bacteriologic examinations. Lesions were compatible with infarcts and were grossly visible as focal, gray-black, red-black, or entirely black triangular areas in the growth plate and proximal metaphysis at the posterior-medial angle of the tibial head. The lesions were detected in 408 of 1000 (41%) tibias that were collected at seven processing plants. Histologic lesions were characterized by thrombosed blood vessels and a well-demarcated focal area of necrosis primarily in the growth plate. No inflammatory cells were present. Massive hemorrhage and cellular debris were common in the necrotic zone, and extensive, fibrin-lined clefts were often seen nearby. Staphylococci and Escherichia coli were frequently isolated from the lesions either in pure cultures or in combination with other bacteria. Histologic evidence suggests that the infarcts were probably traumatic in origin and that the bacterial infection was secondary.

Distribution of arthritis and osteomyelitis in turkeys with green liver discoloration

The distribution of arthritis and osteomyelitis (OM) was studied in turkeys with green liver (GL) discoloration collected in a processing plant; the turkeys originated from seven commercial farms. Overall occurrence of GL, arthritis, and OM in the 25,320 inspected toms was 264 (1.04%), 123 (0.49%), and 107 (0.42%), respectively, and in the 16,690 inspected hens was 24 (0.14%), 0%, and 13 (0.08%), respectively. Prevalence of GL, OM, and arthritis varied among the studied farms. Arthritis and/or OM were detected in 168 (58.3%) of 288 turkeys with green discolored livers. Of the 168 turkeys with OM and/or arthritis, 48 (28.6%) had only arthritis, 45 (26.8%) had OM only, and 75 (44.6%) had both lesions. Arthritis and OM were detected in single and multiple sites and were unilateral and bilateral. Distribution of OM in the 120 OM-positive turkeys with and without arthritis was 77 (64.2%) in proximal tibia, 29 (24.2%) in proximal humerus, 28 (23.3%) in proximal femur, 13 (10.8%) in rib cage, and 4 (3.3%) in distal femur. Distribution of arthritis in the 123 arthritis-positive turkeys with and without OM was 77 (62.6%) in shoulder, 45 (36.6%) in stifle, and 25 (20.3%) in hip joints. Findings in this study suggest that arthritis and osteomyelitis are two distinct lesions and that they may develop independently in the same bird.

Ultrasound for detecting osteomyelitis in turkeys

One thousand turkey legs were examined for osteomyelitis (OM) by ultrasonographic, pathologic, and bacteriologic examinations. OM lesions were recognized as hyperechoic (brighter white) disruptions in cortical bone in the growth plate region by ultrasound examination OM was confirmed histologically in 139 of 1000 legs. OM was detected by ultrasound in 109 of 139 OM-positive legs for a sensitivity rate of 78%. OM was not detected by ultrasound in 713 of the 861 OM-negative legs for a specificity rate of 83%. Ultrasonography was superior to current use of green liver discoloration for detection of tibial OM in turkeys at processing. The economic benefit to the turkey industry from the approval and application of this procedure could be considerable.

Sarcocystis-associated encephalitis in chickens

Sarcocystis-associated encephalitis was diagnosed in a backyard chicken flock that had nervous manifestations. The main histopathologic lesion was necrotizing encephalitis characterized by a large focal area of necrosis infiltrated and surrounded by mononuclear cells, heterophils, and multinucleated giant cells. Schizonts and merozoites were observed in the lesion. Immunohistochemical staining of the brain lesion revealed positive reaction to Sarcocystis antiserum. The ultrastructural characteristics of the parasite were typical of Sarcocystis, including the presence of a nucleus, a conoid, numerous micronemes, and lack of rhoptries. Medication with amprolium and sulfamethazine or with chlortetracycline was not effective in controlling the mortality. Trapping of opossums on the farm and relocating the chickens to clean, new premises seemed to reduce mortality from this infection.

Erysipelas in quail and suspected erysipeloid in processing plant employees

Erysipelas was diagnosed in two commercial breeder flocks of Coturnix quail and was characterized clinically by sudden mortality. At necropsy, lesions comprised generalized congestion, hemorrhages in the thigh and breast muscles, swelling of liver, spleen, and kidney, and dark red edematous lungs. Erysipelothrix rhusiopathiae was cultured from visceral organs of affected birds. Medication with penicillin in the drinking water controlled the mortality. A possible source of infection was fish raised on the premises. Seven people at the quail processing plant developed localized inflammation of the fingers, which responded when antibiotic therapy for erysipeloid was initiated.

Influence of site of inoculation of inactivated vaccines of the immune response in chickens

Commercial caged laying chickens were primed with live Newcastle disease/infectious bronchitis (ND/IB) combined vaccines by spray method at 2, 5, and 9 weeks of age. At 16 weeks of age, birds were inoculated with inactivated ND/1B combined vaccines either intramuscularly, in the breast, wing, or thigh, or subcutaneously, at the back of the neck. An enzyme-linked immunosorbent assay was used to measure serum antibodies to ND virus and IB virus in experimental chickens before injection and every 8 weeks postinjection until 48 weeks of age. The subcutaneous or wing muscle routes of injection resulted in higher antibody titers to NDV through 16 weeks postinjection; however, variations in antibody titers existed among the groups owing to vaccine priming before injection and therefore were not considered important. No differences were found in antibody titers to IB virus among the various groups because of site of injection. Granulomatous lesions were encountered most frequently in birds inoculated in the wing muscle.

Salmonella enteritidis in commercial layer farms in New York state; environmental survey results and significance of available monitoring tests

Seven hundred fifty-one environmental samples were collected from 76 chicken layer houses in a voluntary Salmonella enteritidis (SE) survey study carried out in New York state between January 15 and April 8, 1991. SE was recovered from both houses on 1 farm. Sampling of manure pits and mice in hen houses was useful for SE screening. Phage types of SE from the environment, birds, and mice were identical. The rapid whole-blood test was unreliable, and culture of cloacal swabs was inadequate for detection of SE carriers. Culture of organs from chickens did not correlate well with results of environmental samples.

Studies on transmissibility of a tissue-culture-modified laryngotracheitis virus

The spreading characteristic of a tissue-culture-modified laryngotracheitis virus (LTV) was demonstrated in chickens under both laboratory and field conditions. An enzyme-linked immunosorbent assay was used to measure serum antibodies to LTV in experimental chickens. Contact controls developed immunity comparable to that of vaccinates and were able to resist challenge with a virulent LTV inoculated into the infraorbital sinus.

Studies on the pathogenesis of staphylococcal osteomyelitis in chickens. I. Effect of stress on experimentally induced osteomyelitis

A single strain of Staphylococcus aureus was used to study the pathogenesis of osteomyelitis in chickens. The disease was consistently reproduced in 6-week-old broiler chickens when 1 X 10(5) or more organisms were given intravenously. Severe feed restriction, debeaking, and single or multiple injections of corticosteroids delayed the appearance and decreased the severity of lesions due to staphylococcal infection. This increased resistance was associated with increased numbers of circulating heterophils and monocytes. No correlation between the presence of tibial dyschondroplasia and osteomyelitis was found.

Studies on the pathogenesis of staphylococcal osteomyelitis in chickens. II. Role of the respiratory tract as a route of infection

Groups of 6-week-old broiler chickens were exposed to Staphylococcus aureus by aerosol, intratracheal or intravenous (control) inoculation. No lesions were produced by aerosol. A single dose of up to 5 X 10(10) organisms given intratracheally failed to produce any lesions. Single or repeated doses of 5 X 10(11) organisms given intratracheally resulted in osteomyelitis in a low proportion of chickens.