Iflavirus Covert Infection Increases Susceptibility to Nucleopolyhedrovirus Disease in Spodoptera exigua

Naturally occurring covert infections in lepidopteran populations can involve multiple viruses with potentially different transmission strategies. In this study, we characterized covert infection by two RNA viruses, Spodoptera exigua iflavirus 1 (SeIV-1) and Spodoptera exigua iflavirus 2 (SeIV-2) (family Iflaviridae) that naturally infect populations of Spodoptera exigua, and examined their influence on susceptibility to patent disease by the nucleopolyhedrovirus Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV) (family Baculoviridae). The abundance of SeIV-1 genomes increased up to ten-thousand-fold across insect developmental stages after surface contamination of host eggs with a mixture of SeIV-1 and SeIV-2 particles, whereas the abundance of SeIV-2 remained constant across all developmental stages. Low levels of SeIV-2 infection were detected in all groups of insects, including those that hatched from surface-decontaminated egg masses. SeIV-1 infection resulted in reduced larval weight gain, and an unbalanced sex ratio, whereas larval developmental time, pupal weight, and adult emergence and fecundity were not significantly affected in infected adults. The inoculation of S. exigua egg masses with iflavirus, followed by a subsequent infection with SeMNPV, resulted in an additive effect on larval mortality. The 50% lethal concentration (LC50) of SeMNPV was reduced nearly 4-fold and the mean time to death was faster by 12 h in iflavirus-treated insects. These results suggest that inapparent iflavirus infections may be able to modulate the host response to a new pathogen, a finding that has particular relevance to the use of SeMNPV as the basis for biological pest control products.

Metatranscriptomics and small RNA analysis revealed that viral covert coinfection resulted in disease symptoms reminiscent of rice sterility

BackgroundViral pathogens are a major threat to stable crop production. The discovery of viral diseases traditionally concerns apparent infection that shows obvious symptoms in crop plants. However, little is known about the covert infection of crop plants by viruses. In this study, we used deep metatranscriptomic sequencing and small RNA analysis to identify covert infection of rice plants by viruses.ResultsOur results showed that introgression of the dominant brown planthopper (BPH) resistance gene Bph3 into the high-yielding but BPH-susceptible indica variety Ms55 via a backcross strategy significantly enhanced resistance to BPH. However, Bph3-carrying backcross lines infested by BPH exhibited panicle enclosure and failed to produce seed at the mature stage, which are typical characteristics of sterile rice plants. Using a metatranscriptomic analysis, we identified six RNA viruses in backcross line Rby1 and eleven RNA viruses in backcross line Rby2, including eight novel viruses that fell within existing families and orders. Furthermore, our small RNA analysis revealed the biogenesis of viral small interfering RNAs that represented active virus infection in rice plants.ConclusionBph3-carrying backcross rice lines are resistant to BPH but are susceptible to viral infection. We identified viral covert coinfection in sterile rice plants by deep metatranscriptomic sequencing and small RNA analysis. Our results suggested that covert coinfection of rice plants by RNA viruses resulted in disease symptoms reminiscent of rice sterility. To develop rice varieties resistant to BPH, it is necessary to introgress genes resistant to not only BPH but also viral infection.

Acute respiratory failure

Acute respiratory failure is defined clinically by hypoxaemia with (type 2) or without (type 1) hypercapnia. It is one of the most common problems afflicting critically ill patients and is a common indication for transfer to an intensive care unit. Critical illness may be manifest solely as respiratory insufficiency, especially in patients with covert infection. Acute respiratory failure frequently coexists with other organ system failures in the critically ill, and delayed recognition of the condition adversely affects outcome. The signs of critical illness tend to be similar whatever the precipitating cause and are manifest in failure of the respiratory, cardiovascular, and neurological systems. Full and repeated physical examination may be required to assess the cause and severity of acute respiratory failure and its associated complications, but in severe cases should not delay the instigation of life-saving support and treatment.

Effects of a Covert Infection with Phthorimaea operculella granulovirus in Insect Populations of Phthorimaea operculella

Virus infections of insects can easily stay undetected, neither showing typical signs of a disease, nor being lethal. Such a stable and most of the time covert infection with Phthorimaea operculella granulovirus (PhopGV) was detected in a Phthorimaea operculella laboratory colony, which originated from Italy (Phop-IT). This covert virus (named PhopGV-R) was isolated, purified and characterized at the genetic level by full genome sequencing. Furthermore, the insect colony Phop-IT was used to study the crowding effect, double infection with other PhopGV isolates (CR3 and GR1), and co-infection exclusion. An infection with a second homologous virus (PhopGV-CR3) activated the covert virus, while a co-infection with another virus isolate (PhopGV-GR1) led to its suppression. This study shows that stable virus infections can be common for insect populations and have an impact on population dynamics because they can suppress or enable co-infection with another virus isolate of the same species.

High Prevalence of Covert Infection With Gastrointestinal Helminths in Cats

Fecal flotation is routinely used to identify feline helminth infections in clinical practice, but it is known to have limitations of sensitivity, particularly for cestodes. To determine the prevalence of helminths in a contemporary population of cats and evaluate the ability of fecal flotation to detect these infections, helminths were recovered from intestinal tracts removed from 116 adult cats humanely euthanized by an animal control shelter in northeastern Oklahoma. Results were compared to those of fecal flotation performed using both passive and centrifugal techniques. Helminths were identified in 78/116 (67.2%) cats, including Toxocara cati (48/116; 41.4%), Ancylostoma tubaeforme (8/116; 6.9%), Dipylidium caninum (40/116; 34.5%), and Taenia taeniaeformis (30/116; 25.9%). Cats with T. cati were significantly more likely to harbor T. taeniaeformis (P = .001) than cats without ascarids. Centrifugal fecal flotation with sugar solution identified 37/48 (77.1%) T. cati infections, 8/30 (26.7%) T. taeniaeformis infections, and no D. caninum infections. Proglottids were detected on external examination in 19.0% (12/63) of cats with cestodes. Cestodes were present in over half of the cats examined in this study, but the majority of these infections were not evident by the detection of external proglottids or recovery of characteristic stages on fecal flotation.