scholarly journals Covert Infection of Insects by Baculoviruses

2017 ◽  
Vol 8 ◽  
Author(s):  
Trevor Williams ◽  
Cristina Virto ◽  
Rosa Murillo ◽  
Primitivo Caballero
Keyword(s):  
Covert Infection

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

Viruses ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 337 ◽  
Author(s):  
Larem ◽  
Ben Tiba ◽  
Fritsch ◽  
Undorf-Spahn ◽  
Wennmann ◽  
...  
Keyword(s):  
Virus Isolate ◽  
Phthorimaea Operculella ◽  
Virus Infections ◽  
Full Genome Sequencing ◽  
Double Infection ◽  
Laboratory Colony ◽  
Homologous Virus ◽  
Genetic Level ◽  
Insect Populations ◽  
Covert Infection

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.

scholarly journals The evolution of covert, silent infection as a parasite strategy

2009 ◽  
Vol 276 (1665) ◽  
pp. 2217-2226 ◽  
Author(s):  
Ian Sorrell ◽  
Andrew White ◽  
Amy B. Pedersen ◽  
Rosemary S. Hails ◽  
Mike Boots
Keyword(s):  
Infectious Disease ◽  
Population Dynamics ◽  
Seasonal Variation ◽  
Population Density ◽  
Host Population ◽  
Direct Link ◽  
Birth Rates ◽  
Transmission Rates ◽  
Transmission Success ◽  
Covert Infection

Many parasites and pathogens cause silent/covert infections in addition to the more obvious infectious disease-causing pathology. Here, we consider how assumptions concerning superinfection, protection and seasonal host birth and transmission rates affect the evolution of such covert infections as a parasite strategy. Regardless of whether there is vertical infection or effects on sterility, overt infection is always disadvantageous in relatively constant host populations unless it provides protection from superinfection. If covert infections are protective, all individuals will enter the covert stage if there is enough vertical transmission, and revert to overt infections after a ‘latent’ period (susceptible, exposed, infected epidemiology). Seasonal variation in transmission rates selects for non-protective covert infections in relatively long-lived hosts with low birth rates typical of many mammals. Variable host population density caused by seasonal birth rates may also select for covert transmission, but in this case it is most likely in short-lived fecund hosts. The covert infections of some insects may therefore be explained by their outbreak population dynamics. However, our models consistently predict proportions of covert infection, which are lower than some of those observed in nature. Higher proportions of covert infection may occur if there is a direct link between covert infection and overt transmission success, the covert infection is protective or the covert state is the result of suppression by the host. Relatively low proportions of covert transmission may, however, be explained as a parasite strategy when transmission opportunities vary.

Acute respiratory failure

2020 ◽  
pp. 3867-3880
Author(s):  
Susannah Leaver ◽  
Jeremy Cordingley ◽  
Simon Finney ◽  
Mark Griffiths
Keyword(s):  
Respiratory Failure ◽  
Critical Illness ◽  
Acute Respiratory Failure ◽  
Critically Ill ◽  
System Failures ◽  
Life Saving ◽  
Delayed Recognition ◽  
Covert Infection

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.

Gynecologic Sepsis as a Cause of Covert Infection in Old Age

1983 ◽  
Vol 31 (4) ◽  
pp. 213-215
Author(s):  
MICHAEL A. HORAN ◽  
JOHN A. H. PUXTY ◽  
ROY A. FOX
Keyword(s):  
Old Age ◽  
Covert Infection

scholarly journals Iflavirus Covert Infection Increases Susceptibility to Nucleopolyhedrovirus Disease in Spodoptera exigua

Viruses ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 509
Author(s):  
Arkaitz Carballo ◽  
Trevor Williams ◽  
Rosa Murillo ◽  
Primitivo Caballero
Keyword(s):  
Spodoptera Exigua ◽  
Developmental Stages ◽  
Larval Mortality ◽  
Adult Emergence ◽  
Developmental Time ◽  
Pupal Weight ◽  
Biological Pest Control ◽  
Egg Masses ◽  
Time To Death ◽  
Covert Infection

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.

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