'It could be that there is just a small number of them,' Whitney-Evans suggested hopefully.
Yes,' agreed Major Cormack. 'A small group would be hard to detect in a forest full of wild animals.'
'It's unlikely,' said Lehmann. The life-span of a rat is from fifteen months to two-and-a-half years; the female can have five to eight litters a year with as many as twelve new-born in each litter. She's ready again for mating within hours of giving birth, and the young ones reach the reproductive stage after only three months. You can figure out for yourself just how many could be bred in the space of four years.'
Fender could almost hear the clicking of mental arithmetic going on around the hall.
'I think there's plenty of them,' Lehmann continued, 'but they've gone literally underground. I believe they're in the sewer network beneath the forest; that's where we'll look for them. The perverse thing is that the normal Black rat, or Ship rat as it's sometimes known, is arboreal it can climb trees, high buildings; the mutant has been forced to live below ground. It could explain why they dug up the corpse at the church: they've learned to be burrowers.'
'But that's impossible,' Milton began to say. 'It would take decades for them to evolve ...'
'For any normal animal, yes,' the biologist cut in. We're dealing with the abnormal.'
Thornton spoke. 'So your recommendation is to tackle them at their source: the sewers.'
Lehmann nodded. 'If they're there. We'll pump gas into the network, using a proprietary powder that produces hydrogen cyanide gas when it comes into contact with damp soil or damp air. Our main problem other than attack from the rats themselves will be to block all holes leading from the sewers.'
'I'm afraid many of the sewers have overflowed into some of the streams,' said Whitney-Evans. 'We've complained to the local authorities often enough.'
Those outlets will have to be plugged. We'll need the help of your forestry staff to locate them and any other outlets from the sewers.'
'Perhaps we can help too,' said Milton. 'My staff at the Centre know the forest like the backs of their hands.'
'Fine, the more, the merrier.'
Why not use rodenticides?' the defence secretary asked.
That could be our biggest problem, I'm afraid,' Lehmann said grimly.
There are two main types we could use. One is of the single dose variety: sodium fluoroacetate and fluoro- acetamide, which is normally used in sewers; zinc phosphide;
nor bromide which is harmless to most other animals; arsenious oxide, which is dangerous to most other animals; alpha-chloralose, normally used only against mice. The big disadvantage with these is that rats have a built-in instinct against anything strange to them. We call it neophobia new object avoidance. It makes it difficult to get them to accept new bait. They might try it after a while, but only in small amounts. If they feel any ill-effects at all, they leave it alone completely. A single dose poison might just kill a few, but even that would serve as a warning to the others.'
'And the other type of poison?' the defence secretary asked.
The others are anticoagulants. They kill by their reaction on the rodent's blood system: they interfere with a substance called prothrombin which causes the blood to clot when vessels are broken. The rat suffers a haemorrhage at the slightest damage to blood capillaries: a tiny scratch can kill it. Females having litters are obviously very susceptible.
Three kinds are in current use: Warfarin, coumatetralyl and chlorophacinone. They're administered gradually, building up to a lethal dosage. The rat gets used to the bait, feeds on it regularly, then suffers the effects.'
'And all this takes time,' said Whitney-Evans.
'Yes, but the process can be speeded up. However, that isn't our problem. Over the past few years, rodents in this country have been building up a resistance against anticoagulants. It began in a couple of countries on the Continent, now it's spreading over here. Luke Fender, there, has just returned from the North where he's been investigating the matter. Luke?'
The resistance was first noted in Wales and the Midlands, but now it's spread as far up as Cheshire and down to the south-west coast,' Fender told them. We've bred Warfarin resistant rats in our own laboratories, but these others have developed their own immunity. The point is this: the Outbreak rats had developed that same immunity before gas was used as the final solution. It seems likely that resistance will be inherent in those descended from the rats that escaped from London.
That's why I agree with Mike: gas, providing we can trap them in the sewers, has to be the answer. If the machines can't be relied on to lure them out, we have to keep them in and destroy them there.'
'I think we're all agreed, then,' said Thornton. 'Gas it shall be.
Gentlemen?' he asked the room at large. A murmur of assent was given.
A councillor raised his hand. 'What about disease from these rodents?
How will we combat that?'
'I don't think we need worry ourselves about that problem at the moment,' Stephen Howard said smoothly. The disease caused by the vermin at the time of the Outbreak was a particularly hideous distortion of Leptospirosis or Spirochaetal Jaundice. Fever first, before jaundice set in. The victim became prostrate, blind, then all senses were lost. Coma, then the skin began to stretch and tear, and the victim died. The horrifying thing is that the whole process took only twenty-four hours. Fortunately, an anti-toxin was soon produced, so we needn't fear the disease any more. The other, more normal rodent diseases are too minor nowadays to worry about. No, the main danger it would seem is attack from the beast itself. Of course, everyone 'out in the field' as it were will be wearing protective suits.' Howard reached behind his chair and drew out a large, mounted photograph of a dead mutant Black rat. 'At this stage, I think it might be an idea to remind ourselves just what our old enemy looks like.' He stood, resting the photograph's base against the tabletop so everyone could see.
Fender groaned inwardly. The research director was obviously enjoying throwing the fear of God into his captive audience. No doubt he felt it valuable to impress on them the dangers his company faced. It would make the company bill seem cheap. The move was effective. Fender could feel the shudders run round the room.
'Ugly brute, isn't he?' Howard said jovially. This is actual size.
