Genetically Engineered

The genetically engineered larva, visible only under a microscope, was in her bedroom. No one knows how, or when, it got there. It wasn't created by anything from our planet, and attracted no notice.

Designed to infect female humans, it had a small bulbous head and two tails. It moved slowly by wriggling its two tails in unison, and was hungry for... estrogen. It had been a long time, and it needed to feed.

When the female came home and went to bed, the parasite could smell - no, taste - the estrogen in the air. Slowly it worked over to the bed where she lay and wriggled between the sheets. The scent was much stronger here.

Eventually, the parasite worked up between her legs. She wore no underwear, but it would not have made a difference. Undetected, it slipped between the pussy lips of its future host. The dark, moist chamber made movement easier, and it continued to hunt until it reached an ovary. One of the parasite's tails bore into her egg sack and began to suck microscopic amounts of estrogen from its host. It twitched as the tails began to grow, anchoring itself in place.

The host woke up and went to work, completely unaware of her new companion. During the following weeks, she noticed nothing different. Her period arrived on time, her cramps were unaffected, she had sex with her boyfriend and enjoyed it immensely.

But the parasite's tails continued to grow, and eventually the unattached one was long enough to reach her second ovary. It drilled inside, providing the parasite with another source of food.

Within a few months, the two tails had encased her ovaries with a fibrous mesh that sucked their estrogen and milked them to produce more of the vital hormone. The parasite's head pushed into her vagina and started to develop a characteristic appearance. Her desire for her boyfriend started to diminish, and they fought constantly. They broke up.

And still it grew.

Her ovaries swelled as they strained to produce enough estrogen for the parasite. The fibrous mesh that encased them became thicker and tougher, and then anchored to other ligaments and tendons as well. Two bumps appeared under the parasite's shaft. Her period stopped as the estrogen supply went entirely to feed the growing parasite. Her dreams began to change.

And still it grew.

The head of the parasite appeared between her vulva. Initially shocked, after a few minutes she decided she liked it. It felt like she was being fucked constantly, the soft head rubbing her clit.

She started to play with her new friend. With very little encouragement, the parasite stiffened, shooting white goo all over the bed. She liked the taste, scraping as much as she could off the stained sheets. As she digested the cum, her body began to secrete (in small amounts, at first) pheromones that attracted other women.

And still it grew.

Soon she had what appeared to be a normal sized cock. The small bumps on the shaft morphed into a nice scrotum that pushed itself out of her lady hole, hanging below the shaft as it should.

The parasite's skin that remained within the host's body became thinner and thinner, slowly dissolving in the damp, wet, and warm environment. First, its capillaries merged with its host, exchanging only nutrients. Over time, their circulatory systems became entwined and then indistinguishable as the parasite adapted to its host's blood type and secreted a hormone that prevented rejection. The host's blood pressure was higher than the parasite's, so ever more blood flowed into the parasite, increasing its turgidity.

The parasite became firmer and firmer, and began to fill her thoughts. It was converting all her estrogen into testosterone, driving an unquenchable need. Her breasts and body fat melted away, and her muscles began to develop without effort on her part. She lived on a diet of protein and cum. She fed her cock, and needed it to feed her.

The parasite's flesh began to absorb the woman's clitoris. The tender nerve bundles there became intertwined with the parasite's, increasing both the sensitivity and pleasure that it gave its host. Her vulva fused with the parasite's shaft and nut sack, completing the transformation.

The growth did not stop until her estrogen production maxed out. In her case, she could produce enough for the parasite to reach a total length of 18 inches. Much of its body was anchored inside of her; only 10 inches were exposed. Her balls were the size of tennis balls, and produced an overwhelming amount of cum and testosterone. The parasite's muscles enabled it to spasm intensely during orgasm, spewing cum great distances.

By now it was always erect, and the parasite drove its host to find a mate, several times a day. She could do nothing else. But mates were easy to find. She now looked like a hunk with a big lump in his pants. She lived to fuck, and the pheromones drove prey into her arms. They followed her to bed where she fucked them silly, pumping cum into an eager, welcoming host. Anal and oral sex held no interest. She only wanted fresh pussy. And she found it. Over and over again.

In bed with her victim, the long and fat parasite produced its own lubrication to ease its entrance. Once inside, the intense friction and proximity to unbound ovaries made it wiggle and swell even further. The small lump that remained of the host's clit was in the perfect spot to bump her mate's clitoris as they bottomed out, jolting both with pleasure during the deepest point of penetration. And when the host and parasite climaxed, the parasite's muscles would clench and release, coating the victim's pussy walls with cum.

During the few times she failed to mate in time, she simply leaned over and sucked herself off, draining her swollen balls. Doing so produced more pheromones, increasing the likelihood that she would find a mate next time to relieve herself. It didn't happen often.

But her cum did not contain sperm. It only had more parasite larvae. Nothing existed that could prevent the cycle from repeating itself. Of course, birth control pills had no effect. But even condoms offered no protection. The larvae squeezed between the pores of the plastic to reach their intended goal.

By the time scientists discovered what was going on, no one cared anymore.