Abstract 
 
 We identified the insect iridovirus IIV-6/CrIV as a pathogen of the cricket Gryllus texensis using electron microscopy (EM) and polymerase chain reaction (PCR) analysis. Electron microscopy (EM) showed that the virus attacks the fat body, an organ important for protein production, immune function and lipid storage. During infection the fat body hypertrophied, but egg production withered, leaving the lateral oviducts empty of eggs; the females were effectively sterile. EM of the testis of infected males suggests that the testis was not invaded by the virus, although sperm taken from the spermatophores of infected males showed little or no motility. Nevertheless, males and females continued to mate when infected. In fact, infected males were quicker to court females than uninfected controls. The virus benefits from the continued sexual behaviour of its host; transmission studies show that the virus can be spread through sexual contact. Sickness behaviour, the adaptive reduction of feeding and sexual behaviour that is induced by an activated immune system, is absent in infected crickets. Total hemolymph protein is reduced, as is phenoloxidase activity, suggesting a reduction in immune protein production by the fat body. The evidence suggests that during IIV-6/CrIV infection, the immune signal(s) that induce sickness behaviour are absent. Curtailment of a host's sickness behaviour may be necessary for any pathogen that is spread by host sexual behaviour. ||||| Like sick humans, sick crickets are usually lethargic, lose their appetite and show a decline in their sexual motivation. (Shelley Adamo) 
 
 It's a sexually transmitted disease worthy of a horror movie, one that renders its victims — crickets — infertile, but ramps up their desire to mate. 
 
 The virus IIV-6/CrIV devastated the cricket colony in a lab at Dalhousie University in Halifax. Biologist Shelley Adamo said by the time she noticed a problem, her entire colony had become infected. 
 
 The problem was that the crickets didn't show any of the usual signs of being sick. Like sick humans, sick crickets are usually lethargic, lose their appetite and show a decline in their sexual motivation. 
 
 "What really piqued my interest was that these infected crickets seemed perfectly normal," Adamo told CBC Radio's Quirks & Quarks in an interview that airs Saturday. 
 
 Well, almost normal. One normal behaviour they no longer engaged in was laying eggs. 
 
 Adamo opened up a female to figure out why. 
 
 Both males and females infertile 
 
 "That's when I noticed they were grossly abnormal," she recalled. "Their ovaries were shrivelled up and empty and they were filled with basically their fat tissue." 
 
 An analysis of the fat tissue showed it was "absolutely packed with viral particles." 
 
 The males didn't get away either. While their testes were intact, the sperm inside showed "little or no" ability to move. 
 
 Despite all that, the crickets showed no decline in their desire to mate. 
 
 "Not only did they have no decline, but the males in particular showed increased sexual motivation," Adamo recalled, noting that they started approaching and courting females far more quickly than healthy crickets. 
 
 "We're pretty confident these males are sterile, so the increase in sexual motivation can't really be benefiting them," Adamo said. "But … it can be helping the virus." 
 
 Experiments showed that the virus could be transmitted from cricket to cricket during mating or even during courtship rituals. 
 
 Adamo said the virus can ultimately kill its host. Interestingly, while it does infect young crickets, it doesn't normally kill them until they become sexually mature. 
 
 "They are living long enough to mate, which means they're living long enough to spread that virus." 
 
 All this leads to a sinister conclusion — that the virus may be altering the behaviour of its hosts in order to spread. That is something many parasites are known to do, but not in this particular way. 
 
 Like this virus, many parasites also make their hosts infertile so that energy normally used for reproduction of the host can be redirected to the reproduction of the parasite, Adamo noted in a Dalhousie University news release. 
 
 The virus IIV-6/CrIV ​only infects cold-blooded animals, so humans can't catch it. It has actually been known to infect crickets for about a decade, but this is the first time it has been documented to alter the behaviour of its hosts. 
 
 Adamo and her colleagues published their findings in the Journal of Experimental Biology.
– A newly discovered virus boosts the libido, encouraging those infected—that would be crickets, not humans—to have sex more often and with more partners. The highly contagious iridovirus transmits itself via close contact while mating, but not via insemination; it apparently passes from one's antennae to another's mouth. It also turns the insects' guts blue and kills them in weeks, NPR reports. Infected male crickets, identified in a new study, took just three minutes to begin the mating process when introduced to a female, as opposed to the normal 10 minutes. And females, who usually cut back on mating when sick, were just as geared up for a chirping good time. It's not clear how the virus (which also sterilizes the crickets, the CBC reports) controls their behavior, researchers say, though it could influence hormone levels. It could also be that "when animals sense that they are very ill, they sometimes increase their reproductive output," says the study author. "Basically, because they are about to keel over, they might as well go for gold." So does this "cricket STD" relate to the human variety? Only in that the crickets showed none of the usual symptoms of illness, which is similar to how STDs operate in humans. (Click for another study about animals who "mate themselves to death.")