Citrus tristeza virus transmission by the Toxoptera citricida vector: in vitro acquisition and transmission and infectivity immunoneutralization experiments.

Citrus tristeza virus (CTV) is transmitted by several aphid species in a semi-persistent manner with Toxoptera citricida, the brown citrus aphid (BrCA), being the most efficient. As yet, the molecular interactions between the virus and its aphid vectors have not been determined. This is the first report of aphids acquiring CTV from preparations through an artificial membrane and then transmitting it to receptor plants. The BrCA fed across artificial membranes on crude tissue preparations made from CTV-infected bark tissue were able to transmit CTV to virus-free receptor plants at low rates. CTV p20, p27 and p25 proteins, detected by Western blots, were present in all crude tissue preparations from CTV-infected plants. Partially purified CTV preparations were not transmitted by the BrCA in this manner. Infectivity immunoneutralization experiments were conducted where aphids were forced to feed in vitro on three CTV-specific antibodies (p25, p27 and p20) before being placed on receptor plants following a 48h acquisition feed on CTV-infected source plants. There were no differences in transmission rates among the majority of treatments and the control treatments. However, in one infectivity immunoneutralization experiment, the CTV p20 antibodies significantly enhanced CTV transmission compared to buffer only, pre-immune antiserum or no antibody control treatments. This suggests the inactivity of CTV p20 aids BrCA transmission of virions.

Severity of Citrus tristeza virus Isolates from Texas.

Citrus tristeza virus (CTV) isolates collected from the Lower Rio Grande Valley in south Texas and east Texas were characterized using citrus indicators and molecular methods. The citrus indicators were Mexican lime (Citrus aurantifolia), sour orange (C. aurantium), sweet orange (C. sinensis) grafted to sour orange, Duncan grapefruit (C. × paradisi), and Madam Vinous sweet orange, with some CTV isolates additionally indexed using the Texas commercial grapefruit cvs. Rio Red and Star Ruby, and Marrs and N-33 sweet orange. Severity ratings used 11 biotype groups or cumulative mean relative indices. Molecular characterization was carried out using poly- and monoclonal antibodies, seven strain-specific probes and single-stranded conformational polymorphism, and all were based on the CTV major coat protein or gene. All Texas CTV isolates produced vein clearing symptoms on inoculated Mexican lime plants. Over half of the CTV isolates tested were placed in biotype groups IX and X (causing decline of sweet orange on sour orange, seedling yellows on sour orange and grapefruit seedlings, and stem pitting of grapefruit or sweet orange), and one isolate was in biotype I (mild).

Bringing healthcare home.

Home healthcare systems combine medical and social services to allow a frail person as much independence as possible. Such systems are concerned with maintaining family unity and preserving wellness (rather than merely treating sickness). With improved reimbursement policies, home health agencies could provide effective case management and screening mechanisms to prevent unnecessary institutionalization. Providers must be multidisciplinary specialists, and, unlike acute care providers, they must approach the client from the position of a guest in the home. Establishing rapport and a cooperative relationship with the family is critical to the provision of home care. Formal quality assurance programs focusing on structure, process, and outcomes of home care are essential to maintain high quality. Such programs will not be inexpensive, but they can provide high-quality, cost-effective care.