Nazi scientists at the infamous Dachau concentration camp may have planned to use offensive biological warfare on Germany's World War II enemies. Newly found records suggest they made plans to release malaria-carrying mosquitoes from airplanes. (See also: "Malaria-Bedlam in the Blood.")

Biological warfare, the unleashing of disease-carrying living organisms and natural toxins on enemies, dates to antiquity. In World War II, both Allied and Japanese programs investigated and produced microbes to be used as biological weapons. (See also: "World War II Time Line.")

The recently uncovered research protocols from the Dachau concentration camp, reported by biologist Klaus Reinhardt of Germany's University of Tübingen in the December edition of the journal Endeavour, suggest that Germany also had an offensive biological research program, as long suspected.

Although Hitler issued edicts against biological weapons during the war, experts have debated for decades whether such efforts took place in the hidden corners of the Nazi regime. Complicating efforts to pierce the Nazi veil, research into how to defend against biological weapons can look a lot like-and sometimes lead to-efforts to create them. It's the central, dangerous paradox of biological weapons.

Reinhardt suggests that the Nazis did in fact run an offensive biological warfare effort under the cover of a concentration camp entomological institute headed by insect researcher Eduard May, who died in 1956. "My opinion is that May knew that he did offensive warfare research," Reinhardt says.

Mosquito Warfare

In the Endeavour report, Reinhardt cites German government archival reports written by May, in which he called one malaria-carrying mosquito species best for "practical execution" of air-dropping schemes. Research conducted at the institute to test how long mosquitoes could survive in an airplane showed that malaria-carrying Anopheles maculipennis survived far longer than other types in a food-deprived state.

"The idea to grow malaria-laden mosquitoes and drop them on people is not very well documented other than by the words 'growing station' and 'airdropping site,'" Reinhardt said by email. "The equipment May had at hand was actually rather pathetic."

The malarial mosquitoes were unlikely to survive in Germany, given its cold winters and lack of warm swamps.

Dual-Edged Diseases

Gregory Koblentz of George Mason University's biodefense graduate program remains unconvinced of the offensive nature of the Dachau work.

"Research to assess the threat posed by different biological agents and vectors, such as May's research on mosquitoes and malaria, is especially hard to categorize as offensive or defensive," Koblentz says. "Even if May's intent was offensive, it was very preliminary-many steps away from actually producing a viable insect-borne biological weapon."

Proving that Nazi Germany planned biological warfare is difficult, Reinhardt acknowledges, especially given the chaos in Germany at the end of the war.

"With Nazis fleeing, the Allies taking over, and the U.S. engaging in similar research after the war, employing some of the Nazi researchers," Reinhardt says, "any evidence that has remained is quite likely the least incriminating."

Historical Disagreement

Most historians have concluded that the research institute at Dachau, which was founded by order of SS chief Heinrich Himmler in 1942, was defensive in nature. "Any offensive programme was barred by Hitler's interdict against [biological warfare] development," wrote Erhard Geissler in a 1999 report.

Others, such as Yale historian Frank Snowden, have suggested that Germany went so far as to flood marshes in Italy south of Rome in 1943 and then introduce malaria-carrying mosquitoes to the region. Those reports were based on Allied and Italian records.

Concentration Camp

"Why did the SS need an entomological institute?" Reinhardt asks in the study. The answer is lice. On the Eastern Front, the typhus carrier infested both SS personnel and their prisoners.

At Dachau, the site of the institute, the SS used prisoners as slave labor for arms and chemical companies. This "required a basic survival rate among concentration camp prisoners," Reinhardt writes, which meant eradicating lice and rats in the SS barracks, at the camps, and elsewhere.

Meanwhile, Nazi doctor Klaus Schilling was inoculating camp prisoners with malaria, an act for which he was executed after the war. He had plenty of malaria-carrying Anopheles mosquitoes for experiments.

In 1942, May proposed studying lice, malarial mosquitoes, and houseflies, all disease-carrying insects. Much of the entomological research at Dachau was aimed at eradicating pests, Reinhardt says, but some "was clearly war-related," he concludes.

Outside experts, however, largely see the findings as continuing the debate over Nazi biowarfare plans, not settling it. UPMC Center for Health Security expert Eric Toner says that the Endeavour study "makes a good case" that biodefense research took place at Dachau.

"But I do not see the 'smoking gun' that proves that case for offensive bioweapons research," Toner says. Untangling defensive from offensive research, he suggests, remains a tough question for history to solve.