Can intestinal worms survive when their host receives food only through an intravenous line?

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Two groups of rats were kept on an oral diet after infection with either 10⁴ Trichinella spiralis larvae or 10 Hymenolepis diminuta larvae. At 16 days after H. diminuta infection and 2 days after T. spiralis infection, 8 rats from each group were switched to intravenous (iv) alimentation. The remaining animals continued oral nutrition as controls. Rats were killed during the following 21 days.

Significantly more T. spiralis were recovered from iv-fed rats than from controls, while worm sex ratio and size were similar. Deficiencies in disaccharidases—enzymes that break down disaccharide sugars—normally associated with either infection or parenteral feeding were additive in infected rats receiving parenteral nutrition. The increase in peroxidase activity normally associated with intestinal trichinosis was smaller in iv-fed rats (P < 0.05).

Intravenous feeding did not affect H. diminuta tapeworm numbers, but caused destrobilization, or loss of the segmented body. This was followed by secondary proglottization, the formation of new segments. The worms developed to normal length and had gravid, egg-bearing segments, but their length-to-weight ratio was increased.

The authors concluded that depriving the host of oral food does not adversely affect the development of established T. spiralis. They suggested that the larger worm burden in iv-fed rats may reflect reduced inflammation normally involved in worm expulsion. They also concluded that food entering the gut from outside is not necessary to maintain established H. diminuta: the worm can obtain all factors needed for sustenance and growth from the exocrino-enteric circulation, through the host’s exocrine secretions into the intestine.