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THURSDAY, JULY 23, 2026   |   SPECIAL REPORT & ANALYSIS

ANIMAL HEALTH  |  NEW WORLD SCREWWORM

Screwworm Case Count Climbs to 42 as a New Sutton County Detection Keeps the Summer Front Alive

A July 21 confirmation in goats becomes the third case in a single Edwards Plateau county, even as every case from June is now listed as inactive.
 

Analysis  ·  July 23, 2026

A new detection of New World screwworm (NWS) in goats in Sutton County on July 21 has pushed the U.S. case tally to 42, according to USDA’s Animal and Plant Health Inspection Service (APHIS) — and it lands at a moment when the outbreak is doing two things at once: resolving where it started in June and re-igniting in a tight southwest Texas cluster through July.

Where the outbreak stands

The cumulative count of 42 confirmed cases masks a sharp split between the two months of the outbreak. Of the 42 total, 31 were confirmed in June and 11 in July through the 21st. Every one of June’s 31 cases is now listed as inactive — meaning the infested wounds have been treated and closed and the animals are no longer considered a live source of larvae. July is a different picture: 10 of the month’s 11 cases remain active. Netted out, the active caseload the country is managing right now is small and almost entirely a July phenomenon, but it is concentrated and it is not yet slowing.

The distinction between active and inactive is central to reading these numbers. A case is counted as active until the wound is fully resolved; an inactive case is not a new all-clear for a region so much as confirmation that a specific animal’s infestation has been closed out. That is why a rising cumulative count can coexist with a shrinking active count — and why the July cluster, not the June total, is where the epidemiological attention sits.

Table 1. Case tally at a glance as of July 21, 2026. Source: USDA APHIS.

A cluster tightens across the Edwards Plateau and Trans-Pecos

Geography is the other half of the story. With the exception of a single July 17 case in Starr County, on the South Texas border, every active case sits in a compact block of the Edwards Plateau and Trans-Pecos: Sutton, Crockett, Pecos and Brewster counties. This is ranch country — extensive cow-calf, sheep and goat operations spread across large, lightly fenced pastures — which is precisely the landscape in which a wound-seeking parasite can move animal to animal before it is caught.

Figure 1. Active NWS case clusters in Texas as of July 21, 2026. The four-county southwest cluster is shown in blue; the lone Starr County outlier in gold. Source: author analysis of USDA APHIS case reports; county boundaries via U.S. Census.

Figure 2. A closer view of the southwest Texas cluster and the Starr County outlier. Source: author analysis of USDA APHIS case reports; county boundaries via U.S. Census.

Table 2. Where the active cases sit. Source: USDA APHIS.

Sutton County becomes a focal point

No county illustrates the outbreak’s arc better than Sutton. It has now recorded three cases spanning both months, and two of the three are active. The first — confirmed June 12 in sheep — is inactive, a clean close-out that fit June’s pattern. But the July 13 detection in a dog and the July 21 detection in goats are both active, making Sutton the clearest example of a place where the parasite has appeared, been resolved, and then reappeared within weeks. The involvement of a dog alongside livestock is a reminder that NWS is not choosy about host species; any warm-blooded animal with an open wound is a candidate.

Table 3. Sutton County case timeline. Source: USDA APHIS.

July is a tale of two trends: June’s 31 cases have all gone quiet, even as 10 of 11 new July cases stay active — a caseload that is closing out and renewing itself at the same time.

The month-over-month split

Laying June and July side by side shows why officials can report both progress and persistence in the same breath. June’s cohort has been fully worked down to zero active cases; July’s has barely begun to resolve. If July follows June’s trajectory, its active count should fall over the coming weeks — but that is a projection, not a result, and the fresh Sutton detection shows new cases are still entering the system faster than the July cohort is clearing.

Table 4. June versus July, by status. Source: USDA APHIS.

The surveillance signals worth watching

Two negatives in the APHIS reporting are, for now, the most reassuring numbers in the file. 

First, there are still no confirmed cases in wildlife or feral animals. That matters more than it may sound: the nightmare scenario for eradication is the parasite establishing itself in a free-ranging wild host population — deer, feral swine — where it cannot be treated animal by animal and can sustain itself indefinitely. As long as detections stay in owned, observable livestock and pets, the outbreak remains something responders can physically reach and close out.

Second, there are still no NWS detections in the fly-trapping network. Trap catches are the early-warning layer that would signal free-flying adult populations establishing on U.S. soil rather than isolated infestations arriving on individual animals. Their continued silence suggests the July cluster, however stubborn, is not yet evidence of a self-sustaining fly population taking hold in the Edwards Plateau.

The national backdrop: a sterile-fly buffer

The Texas cases sit inside a much larger federal containment effort. As the parasite has pushed north through Central America and into Mexico over the past two years, APHIS has leaned on the sterile insect technique (SIT) — the same biological weapon that eradicated NWS from the United States by the 1960s. Sterile male flies, mass-reared and released, mate with wild females, which mate only once; the resulting eggs never hatch, and a saturated release collapses the wild population. USDA has been dispersing on the order of 100 million sterile flies a week and has moved aircraft and insects to reinforce a buffer roughly 50 miles into Texas near Tamaulipas, Mexico. Sterile pupae are dyed so released flies fluoresce under UV light, letting inspectors separate program flies from wild ones in the trap line.

Against that backdrop, the July cluster reads as exactly the kind of incursion the border strategy is built to catch and contain: real, worth taking seriously, but so far confined to treatable domestic animals well inside the surveillance envelope rather than a breakout of wild, self-sustaining flies.

Bottom line

The screwworm count reaching 42 is less alarming than the raw number suggests — and less benign than it looks. June’s 31 cases are all resolved, but 10 of 11 July cases remain active and are tightening into a four-county southwest Texas cluster, with Sutton County now on its third detection. The encouraging signals — no wildlife cases, no trap catches — mean the outbreak is still where responders can reach it. The figure to watch is not the cumulative 42; it is whether July’s active cluster resolves the way June’s did, or whether new detections keep outrunning the close-outs.