Remedies for Treating Screwworm Larvae

by Douglas Fodge



We had chased the bull calf all over the pasture until we panted like one of Daddy’s hounds on a hot day, but still the calf couldn’t be cornered and caught. I suppose he suspected that he wouldn’t like what we had in store for him that afternoon! We had discovered that the calf had a bad wound on his belly, probably on his naval, and the wound was teeming with the maggots (insect larvae). A frothy, bloody discharge appeared on the surface surrounding the wound, and up close the stench emanating from the open site was pretty strong. If left to the designs of the screwworm larvae, the calf would soon be a part of history. We had to do something, and fairly rapidly at that, and there was no time to wait several days for the arrival of a Vet, moreover we had little or no money to spend on his services.

Screwworm larvae represented the parasitic stage in the lifecycle of a fly (now named Cochliomyia hominivorax), and prior to about 1960 they, and close kin, caused severe damage to domestic and wild animals, and infrequently people (most frequently the nasopharynx tissues), across Texas and much of the south. These flies were nearly twice the size of the common housefly. More than 100,000 species of two-winged fly species had been identified by the 1950s, and several attacked animals. Myiasis was the veterinary term for a fly strike, and each species of fly had a slightly different mode of attack, a different life cycle and a different range of occurrence. Some flies attacked rabbits (Cuterebra sp or Dermatobia hominis), others deer etc., but if any of the troublesome species laid eggs near open wounds on animals, the eggs had plenty of rich nutrients for their needs. Of all of the species, the screwworm fly was the worst one because each individual female fly could lay perhaps 500 eggs, and the eggs hatched shortly thereafter.

The eggs quickly changed (metamorphed) into larvae and migrated into a wound. These beasts had strong mandibles for chewing that were complimented by an enzyme-laden digestive system, and they were capable of destroying an animal, inside out. Wounds did not need to be elaborate and could be caused by anything from a scratched insect bite or a thorn’s penetration of an animal’s skin, no matter how slight it may have seemed. An animal’s navel or a thorn penetration (holes) usually concealed the extent of the problem, but surface wounds could easily be enlarged from simple scratches to large holes by the larvae. It was rumored that screwworm flies carried infectious bacteria and viruses, and perhaps other things as well, but the big problem with them were the larvae. Left unattended, screwworm maggots could kill an animal in less than 2 weeks, and during that time thousands of the larvae would mature into pupae, leave the wound and burrow into the topsoil where the fly’s lifecycle was completed. This species was an obligate parasite (to complete their life cycle the larvae could only develop in wounds of animals). Fortunately, by the mid 1960s, screwworm flies were eradicated as far south as Central America when the USDA (U.S. Dept. of Ag.) released X-irradiated, sterile, male flies. When these males mated with females, their offspring did not lay fertile eggs and the life cycle was stopped in its tracks.

Navels were particularly vulnerable sites for screwworm flies to lay their eggs, and the bull calf was a prime example of this since his navel was teeming with the maggots. After about 15-30 minutes of chasing the calf, we finally cornered and downed him. Daddy tied the calf’s back feet together and sat on them, and I lay across his front legs and held his head on the ground. I don’t know who was worse from the chase, the calf or me, but at least I wasn’t about to be worked on, and he was. I suppose that had a Vet attended to the calf’s miseries, he would have used sterile, stainless steel instruments to make the corrective measures that were necessary, but we didn’t have any of those. Daddy had his pocketknife, and it certainly wasn’t sterile, but neither was the wound.

With the knife Daddy cut a small hardwood limb and removed the bark and limbs from it. Then he fashioned a small hooked point on one end of the tapered stick. This foot-long stick was used to dig the maggots out of the wound, and since there were hundreds, if not thousands in the wound, the process to snare the maggots one-at-a-time and pull them out of the decaying flesh was lengthy, estimated at 30-45 minutes. Although the screwworm maggots would have eventually killed the calf, maggots of some other species have been used, even in modern times, to clean out a wound leaving it almost bacterial- and fungal-free. However, the medical community used maggots raised under aseptic conditions for this practice, rather than allowing some flies to blow the wound! After fishing maggots out of the wound, Daddy decided that he had cleared out enough of them to take the next step in the treatment process.

Any time we treated an animal for screwworm infestations, we were concerned and uncertain that all the maggots had been removed, much less any other contaminating microbial species. Therefore, the next procedure was aimed at killing any leftover maggots and preventing a second infection before the wound healed. On a farm there were plenty of other marauders (blowfly species of the genera Lucilia, Calliphora, Phormia, and Chrysomyia ) awaiting the attractiveness of an open wound, and any number of them were capable of introducing infectious agents to the site if they got the chance, although these flies were not obligate parasites and did not need to lay eggs in wounds to complete life cycles. Out of his pocket Daddy produced his omnipresent bottle of inexpensive disinfectant (coal oil, kerosene), and he doused the interior and exterior surface surrounding the wound with this solution. Coal oil was used to disinfect anything that needed to be disinfected on our farm. Then he smeared (Product 66, a Balm or Salve of unknown commercial sources) a tarry product about one-half inch deep on the inside and outside of the wound. The balm was composed of things to disinfect the wound, and it had a black, thick consistency, and I doubt that anything could penetrate it. For all I know, it may have been asphalt, but it didn’t have the consistency of asphalt and didn’t need to be heated before use. Since we didn’t have suturing materials, the calf was let loose, complete with an open wound covered thoroughly with this product. The calf recovered pretty nicely, and when we sold him that fall he brought a decent price.

Maggots did not have lungs, but they needed oxygen for survival. Since there weren’t lungs to inspire the air and oxygen, the maggots relied on a series of tubes (spiracles) located on their posterior surface to breath the air. These tubes carried air to the interior of the worm, and if any substance clogged the spiracles the maggots would be suffocated. I am confident that Product 66 killed maggots because it clogged their breathing apparatus, and they suffocated in the process. Many farmers used any oily substances that were available, ranging from axle grease, motor oil, mineral oil and even cooking oils to coat the interior of wounds that contained screwworms. According to my cousin James R. Miller, Uncle Jack often mixed some sulfur with Vaseline, and used this mixture to treat cattle for screwworm infestations. Since it contained sulfur, it probably also inhibited microbial growth in the wounds.

Cattle weren’t the only animals that suffered screwworm infestations, and on other occasions we treated various farm animals that had an infected wound, usually started as a small cut. One special animal that we treated was one of Daddy’s priced foxhounds that suffered either a cut or scratched the skin on his scrotum. We suspected that it occurred while the dog tried to clamber through a barbed wire fence, but as talented and well trained as Daddy’s hounds were, they couldn’t talk, and we never knew what happened. Sure enough in a few days after suffering this indignity, flies of some species laid eggs near the wound and within hours the foxhound, and we, had a big problem. However, catching one of Daddy’s hounds could be difficult even when they were healthy, and this one avoided us for more than a day before we finally caught him. Some of Daddy’s hounds were practically wild animals, and I recall vividly one prized Beagle, Buck, who lived at our house for 12 years, eventually dying of old age, and Mama’s hand ever laid on him during the 12 years, and she caught him only twice after he had been injured in some hunting incident and didn’t run away from her. By the time we caught Daddy’s foxhound with the infestation, the maggots had already done considerable damage. As rapidly as possible, we repeated the procedure that we had used on the calf, and the hound recovered after a few weeks. Eventually the hound was carried on hunting trips and he began to hunt at a level up to his previous standards.

Following the foxhound’s successful show of vigor in the hunts, Daddy began to wonder if the foxhound had suffered permanent sterility (castration) from the larval infestation. As soon as a female was available, Daddy penned the foxhound in a kennel with a female in estrus to test his virility. In due time, we had evidence that the foxhound was fully recovered. The female gave birth to a fine litter of healthy pups, and many of them became fine foxhounds.

While the field surgery procedures described herein were gruesome and seem primitive by modern standards, others in the region practiced them just as we did, and similar procedures are still used today in many areas of the world. They worked almost every time. Nonetheless, screwworms took a major toll on cattle ranches and farms across Texas and the region, and as mentioned previously, screwworm infestations often went undetected until it was too late to save an animal. Experts in modern Vet Schools have estimated that an outbreak of screwworm flies, similar to those of the first half of the 20th century, would cost the US cattle industry upwards of nearly $1 billion per year, not to mention the impact that such an outbreak would have on other animal production industries. While such an outbreak is unlikely, should such an occurrence happened, I take comfort in the knowledge that one procedure would be available to help save animals, at least for those of us old enough to recall the treatment.

Ice Cream On A Sunday Afternoon

by Douglas Fodge



The peach trees were almost collapsing under the weight of fruit, and I was licking my chops in anticipation, but not just for ripe peaches. The entire extended family was waiting for an invitation from Aunt Evie (AE) and Uncle Carl (UC) to sample some peach ice cream over at their home. Ice cream at their home was a warm weather routine and a fine social event, but they usually made ice cream with bananas in it. That is, until local peaches started ripening. Now, mind you, I ate ice cream at lots of other local homes, but theirs was tops on my chart. At the time I didn’t have a clue about why I liked theirs better than other ice creams I ate, but I am finally beginning to understand.

UC and Daddy were brothers and AE and Mama were sisters so we had almost a double-whammy set of parents, and three double-first cousins thrown in for good measure. Casual observation pointed out the differences more than the similarities of the four. The major difference between Mama and AE were size and temperament; otherwise they had lots of similar interests and motivation levels. Both women loved music, reading and could lecture on many subjects with little provocation. Neither of them tolerated foolishness very well, but both had great a sense of humor and fine intellects. On the male side, physical appearances were slightly apparent since Daddy had smooth facial skin, but UC’s face was wrinkled to the maximum extent possible. Had all of the wrinkles been flattened, UC’s face might have been at least half-again its size. However, the depth of each wrinkle was an appropriate reflection of UC’s kind and gentle nature. It wasn’t so much that Daddy was unkind or not gentle, but he was so absorbed in his hobbies of hunting and fishing that he was sometimes unaware of things around him – focused, focused, focused on catching the game, spare no life or limb. Daddy trained hounds and possessed general hunting skills that were second to none of his local hunting buddies. He had little interest in anything mechanical or electrical although he was a decent gardener. In marked contrast, UC had zero interest in hunting and fishing, but he constructed mechanical garden tools. This was before you could run to Home Depot and buy them. He built something with lumber regularly, and all devices worked well for the intended purpose. For example, UC built the house where I was born, assisted by Daddy. Both men and Uncle Bob, their younger brother, were skilled musicians, and I remember hearing all three of them whistling tunes while they worked, and they whistled on key at that. Mama and AE could also whistle pretty well, but they primarily sang hymns when they worked. The women had more formal education than the men, but all were smart. Ice cream making was one of those areas where AE and UC made their mark, at least as judged by me. Theirs was the best ice cream in the region as far as I was concerned, but then no one ever accused me of possessing discriminating taste buds or having unbiased opinions.

For most of the kids, the consumers, ice cream was merely a delicious frozen treat, and they paid scant attention to the process involved in the making. We were usually too busy eating ice cream and playing card games or croquette to bother with such details. However, I recognized even as a kid that the ice cream I ate at numerous other homes around our community just wasn’t up to snuff (acceptable quality). My interest in this subjective conclusion resulted in a lifelong curiosity and prompted an occasional investigation to attempt to explain why I thought their ice cream was better than others. The investigation got rolling when I was in college and has continued intermittently through the years. Partly having to take physics classes and eating homemade ice cream ‘round the world, much of which didn’t live up to their standards, fueled my investigation. Most homemade ice creams had too much fat in them and were not light and fluffy – things I expected in ice cream when we ate UC and AE’s product.

AE & UC’s prowess in making ice cream was probably self-taught, and I’m pretty sure he couldn’t explain any of the physics, but AE might have given it an A for effort. Had a food technology textbook been available UC probably wouldn’t have read it since he had really poor eyesight and didn’t care that much for reading. For example, after their offspring left home as adults, Jim Curry or I often traveled with UC when he made trips to new customers. UC drove a truck, and due to his poor eyesight he wanted someone to go along on the first trips to help find and read the signs. These were the days prior to modern freeways with well-lighted signs. He could have read the signs, but he wore really thick eyeglasses that weren’t amenable for darting your line of sight all over the place, especially at nighttime, to find the signs. Afterwards, he didn’t need to find and read signs as the route was memorized. Making homemade ice cream didn’t require 20:20 vision, but to make it time-after-time to the same consistency required fine powers of observation, tasting skills, and a good memory of what did, or did not work well. They certainly mastered this.

To manufacture homemade ice cream an emulsion, foam and dispersion must be formed among the ingredients. If you got all the parts working properly, then you produced an ice cream that had tiny ice crystals, the appropriate amount of dissolved air, and thoroughly distributed and stabilized fat globules. These three areas done properly gave ice cream the appropriate mouth feel and texture. Theirs was the only ice cream I sampled locally with this characteristic. Some years ago I started examining recipes for homemade ice cream, and recently I obtained the following recipe (from Vivian Fodge Patterson, one of our double-first cousins) that was used by AE for preparing their homemade ice cream:

“Mother mixed ½ gallon of whole milk, 1 ½ cups of granulated sugar, a pinch of salt, 3 well-beaten eggs, 1 tsp of vanilla extract. They usually made Banana Ice Cream, and she sliced 3 bananas, added those and then filled the ice cream bucket about 2/3 full to allow room for expansion. Daddy always used blocks of ice because it was harder and didn’t melt as quickly as pre-chipped ice. He chipped the ice block with his ice pick as needed and added the ice and rock salt around the freezer bucket. When the ice cream mixture could no longer be turned with the hand crank, he covered the entire assembly to let it harden for a while. Done with this part, he sat back under the shade tree, rolled himself a Prince Albert tobacco cigarette and relaxed while the cream finished.”

I calculated the amount of fat in AE’s ice cream recipe as being somewhere between 80 and 90 grams/gallon, about 2.5%. This estimate depended largely on the fat content of the whole milk she used, and in those days the fat content could have varied by as much as 20 to 30%, if not more, on occasions when they bought milk from individual farmers who owned Jersey cows. Compared to eight other vintage recipes for homemade ice cream from various parts of the USA, AE’s recipe averaged about 25% less fat and calories and had even less protein than others. Although the eight other recipes in my collection yielded low-fat ice creams, AE’s would have been ultra-low-fat, yet it had superb mouth feel and taste and consistently yielded better ice cream than any I have made.

Unless a commercial producer of ice cream used ultra low-temperature, high-speed extrusion equipment and air-injection systems, it would have been hard for them to easily make a commercial ice cream that was as high-quality as theirs. For decades ice cream manufacturers have used large quantities of whole milk, whole cream and eggs (principal sources of fat and protein in ice cream) to overcome the formation of ice crystals and to produce premium quality ice cream. Some of the homemade ice cream recipes required 9 to 10 eggs/gallon and used Half-N-Half rather than milk. This trend led to the current popular, premium quality ice creams such as Haagen Das or Ben & Jerry’s. For commercial companies, it was probably less expensive to overwhelm the mouth feel and texture by increasing the amount of stabilized fat globules in their products than to pay for the extra processing costs associated with preparing a high-quality, low-fat ice cream. Even today low-fat ice creams sold by premium brand companies aren’t really low-fat compared to AE’s recipe. If the answer was not in the recipe, then what contributed to the superb mouth feel and taste of their ice cream?

As far back as the 1960s, we have been spoiled by icemakers in refrigerators or by a 7-11 on every corner where we purchased chipped ice, or the equivalent of chipped ice. When we were kids there were few such options, at least in our small communities. We purchased ice from an icehouse, and it was either in blocks (25, 50 or 100 lbs per block) or chipped. In our community, the Martin and Norwood families sold and delivered ice to local residents. Generally, the blocks of ice arrived wrapped in discarded newspapers and covered with thick quilts. Once you got it home, the ice was stored in either an icebox or in a tub, and neither was refrigerated. Then we raced against time during the hot weather months to use it before the ice absorbed enough heat from the air and melted. Chipped ice, due to the huge increase in surface area of the chips, was warmer and this was due to the fact that it absorbed heat rapidly and melted much more quickly than block ice. A few times after I was old enough to help him make the ice cream, I went with UC to buy block ice, and he always mentioned to me that we were going to a particular ice house because they had the coldest ice. He never used chipped ice. We brought the blocks of ice home and started making ice cream as rapidly as possible. We chipped the ice as needed to fill the freezer space around the ice cream container, and this meant that the chipped ice he used was a lot colder than most used by others. UC also had a few other tricks that he used to top off the ice cream preparation.

As he added the freshly chipped ice and covered it with rock salt, UC stirred the mixture vigorously for several minutes, almost to the point of building a foam head on the mixture. This rapid churning had a direct impact on the lightness and fluffiness of the ice cream as it allowed a lot more air to be dissolved in the emulsified liquid before it started to freeze. I do not recall others doing this when they made ice cream. Another thing that UC did was also important; he preferred to use the hand-driven ice cream makers rather than electric models. Even if he used the electric models he often had rigged the equipment so that when the electric motor stopped, he could replace it with a hand-crank. Then, he continued to churn the mixture with the hand crank. Once the mixture froze solidly, turning the crank caused the entire assembly to turn. When this happened either Jim Curry or I, or someone of the younger set, were told to sit on the ice cream freezer to help hold it in place so he could continue to churn the mixture. The continued churning motion in the freezing mixture prevented the formation of large ice crystals (coarseness) in the last part of the cream that froze, that portion that is the most concentrated with sugar and fat globules. He also prevented air from escaping the product. Thus, part of UC and AE’s success undoubtedly was related to their understanding that he could overcome the low fat, protein and sugar content of the recipe if he kept turning the crank long after others stopped. If they used fruit in the preparation, then the additional churning motion was even more important.

In this day and age of behemoth football players and exaggeration of size in men, it is worth mentioning that UC weighed about 160 lbs (with rocks in his pockets), but he had an advantage over lots of his contemporaries. These were the times before forklifts were widely available, and as a truck driver delivering heavy construction lumber he had to unload and stack the lumber at a customer’s office, all by hand. Several of us can testify to the fact that it was a rare event when the customers provided someone to help unload the truck. One 2” x 12” x 16’ piece of freshly cut, moisture-laden piece of oak weighed perhaps 125-150 pounds, and 8” x 8” x 12’ posts weighed even more. The trailer was about 32 feet long and stacked with hundreds of these things. Thus, if a fellow unloaded and stacked a few truckloads of these every workday, what resistance could a little hand crank on an ice cream machine possibly offer? What better testimony to their intelligence I cannot imagine than their ability to independently determine how to consistently produce superb ice cream.