Announcement

**Shiloh** · May 8, 2025, 01:54 PM

Source: https://evrimagaci.org/tpg/mexico-co...rewworm-346321

08 May 2025
Mexico Confirms First Human Cases Of Myiasis From Screwworm
Two individuals in Chiapas affected by parasitic infestation linked to livestock, raising public health alarms.

In a concerning public health development, the Secretaría de Salud (SSA) of Mexico has confirmed two cases of human myiasis caused by the livestock screwworm, a parasitic infestation that has emerged in the southern state of Chiapas. The affected individuals, a 77-year-old woman from Acacoyagua and a 50-year-old man from Tuzantán, are the first reported human cases of this condition in the country, raising alarms about the potential spread of this disease.

The first case involves the elderly woman, who has a history of untreated diabetes. She suffered a fall on March 31, 2025, leading to a head trauma and a wound in the right parietal region. After experiencing fever and no improvement from home remedies, she sought medical attention on April 11 at the Hospital Rural Bienestar de Mapastepec. During her hospitalization, it was discovered that she had been in contact with livestock, including a goat and a calf that had shown signs of infestation. Surgical procedures revealed a 3x3 centimeter wound with visible larvae, confirming the diagnosis of myiasis caused by Cochliomyia hominivorax.

The second case is of a 50-year-old man who developed symptoms starting April 19, 2025, after a dog bite on his left leg. He noticed larvae emerging from the wound on April 23, accompanied by intense pain, fever, and erythema. He finally sought medical help on April 25 at the Centro de Salud de Huixtla, where six larvae were extracted, confirming the presence of the screwworm infestation.

Both cases were reported between April 15 and April 25, 2025, according to the Epidemiological Bulletin of Week 17 released by the SSA. The presence of myiasis in humans is more common in rural areas, particularly where there is close contact with infected animals. The SSA has noted that an increase in cases of animal myiasis can lead to a corresponding rise in human cases...

**Pathfinder** · May 9, 2025, 10:29 AM

Translation Google

Epidemiological Week 17

https://www.gob.mx/cms/uploads/attachment/file/996426/sem17.pdf

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From the PDF link above:

Epidemiological Surveillance Week 17, 2025

Report of human cases of myiasis caused by larvae of Cochliomyia hominivorax (Cattle Screwworm) in Mexico during 2025

Introduction

Cutaneous myiasis is a parasitic infestation of the skin caused by the larvae of Cochliomyia hominivorax, a blue-green fly ranging in size from 10 to 15 mm. Its larval stage, known as the Cattle Screwworm (CSHW), is an obligate parasite that exhibits a tropism for the tissues of warm-blooded animals, including humans (1).

The predatory activity of the larvae on the skin and underlying tissues of the host leads to a condition called traumatic myiasis, which can be associated with high morbidity and mortality. Acquisition of the infection usually occurs in sites with previous interruptions in the continuum, whether accidental or iatrogenic (associated with livestock farming practices); however, involvement of the mucous membranes of natural body orifices has also been documented (2).

Female C. hominivorax mates only once in its life cycle and is highly fecund, capable of laying up to 4,000 eggs. These females can disperse up to 50 km from their site of origin and can be transported even longer distances by attaching themselves to vehicles or other means of transport. Eggs are laid in groups of between 12 and 400 on the skin surface of the host. Larval hatching occurs within a few hours, after which the larvae begin feeding on host tissue. After four to eight days, the larvae detach from the host and burrow shallowly into the soil to undergo metamorphosis into pupae. Emergence of adult flies occurs in approximately one week under warm and humid climates, but this period is longer in temperate climates (1-2).

The GBG is considered endemic in tropical and subtropical regions of the Americas, including several countries in South America, Cuba, Haiti, and the Dominican Republic. The following populations are identified as at greatest risk (3):

 Residents of rural areas in regions or countries with endemicity for the New World Screwworm and where livestock farming is practiced.
 Individuals whose work involves frequent contact with livestock.
 People with skin wounds, including recent surgical wounds.
 Vulnerable populations, such as immunocompromised individuals, those at the extremes of life, and people with malnutrition.

Myiasis in humans shares clinical characteristics with those observed in animals. In addition to myiasis associated with wounds and ulcers (such as those of varicose vein origin on the lower limbs), it can manifest as furunculoid myiasis, characterized by the appearance of an immobile cutaneous nodule. Myiasis of natural cavities is, in most cases, secondary to infestation by C. hominivorax larvae. Invasion of the nasal passages (rhinomyiasis) is the most common presentation and usually occurs as a complication of chronic atrophic rhinitis (ocena).
C. hominivorax larvae can destroy cartilage and the palatine vault,
and can spread to the paranasal sinuses and even reach the cranial cavity. Ocular involvement can result in destruction of the eyeball (1,3).

EPIDEMIOLOGICAL SITUATION IN MEXICO.

GBG disease was a problem in Mexico until 1991, when the states of Tabasco, Campeche, Quintana Roo, and Yucatán were declared pest-free. On September 9, 2003, the state of Chiapas was declared pest-free (4).

On November 23, 2024, the Ministry of Agriculture and Rural Development notified the World Organization for Animal Health (WHO) of the first confirmed case of GBG in a foreign-origin cattle, intercepted in Catazajá, Chiapas. From November 21, 2024, to April 18, 2025, the National Service of Agrifood Health, Safety, and Quality (SENASICA) has confirmed 869 cases in animals: 487 in Chiapas, 249 in Tabasco, 116 in Campeche, 13 in Quintana Roo, and four in Yucatán (4).

CLINICAL CASE REPORT.

On April 15 and 25, 2025, the Chiapas State Health Services reported probable cases of unspecified demycosis.

Case 1.
This is a 77-year-old female patient, a resident of the municipality of Acacoyagua, a homemaker,
with a history of diabetes mellitus diagnosed two years ago, with no treatment or medical follow-up. The patient began experiencing symptoms on March 31st, following a fall from her own support plane, which caused a head injury and a wound in the right parietal region. She did not seek medical evaluation, but was treated at home with the help of a neighbor, but showed no improvement. On April 10th, she developed a fever, and on April 11th, she went to the emergency room of the Rural Well-Being Hospital in Mapastepec, where she was hospitalized due to the degree of infection in the wound. During the interview, the patient reported living with cattle and dogs, mentioning that a goat and a calf had developed a "worm infestation" in the navel two weeks and five months prior, respectively.

On April 13, surgical lavage and debridement were performed, revealing a 3x3 cm wound in the right parietal region, with exposed bone with no apparent fracture trace, dissected to a distance of 6 cm around the wound, and the presence of myiasis, which could not be recovered. On April 16, another surgical lavage was performed, yielding two larvae, which were sent to the National Reference Center for Animal Parasitology and Analytical Technology of the National Service for Health, Safety, and Agrifood Quality (SENASICA), where the diagnosis of C. hominivorax demiasis was confirmed on April 17. On April 18, the patient was transferred to the "Ciudad Salud" Regional High Specialty Hospital and reported as stable.

Image 1. Lesion and larvae obtained from the first case of C. hominivorax in Chiapas, 2025.
...
Case 2.
This is a 50-year-old male patient, a resident of the municipality of Tuzantán, a rural occupation. The patient's symptoms began on April 19th, following a dog bite on his lower left limb, without seeking medical attention. On April 23rd, he observed larvae emerging from the wound, accompanied by a sensation of movement, intense pain, erythema, and fever. However, he did not attend Tuzantán municipal services until April 25th, from where he was referred to the Huixtla Health Center, where six larvae were removed. SENASICA personnel performed a taxonomic telediagnosis, confirming C. hominivorax myiasis. Samples were also sent to the State Public Health Laboratory for taxonomic confirmation by the Ministry of Health. The patient was referred that same day to Huixtla General Hospital for surgical lavage of the wound.

EPIDEMIOLOGICAL SURVEILLANCE.

When a probable case of myiasis caused by C. hominivorax is identified in a primary, secondary, or tertiary care unit, the following activities should be carried out in accordance with the "Manual of Standardized Procedures for Epidemiological Surveillance of Myiasis by Cochliomyia hominivorax in Humans":

 Identify wounds infested with larvae, clean, and disinfect them.
 Immediately notify (within the first 24 hours) the health jurisdiction and the immediately superior level of your institution, attaching the epidemiological case study. The health jurisdiction and state epidemiology department must ensure immediate notification of the case by sending the epidemiological study to miasisgbg.humano@salud.gob.mx.
 Collect preferably ten larvae from the deepest part of the lesion or flies, polypropylene bottle properly labeled, in 70% alcohol, specimens in adult phase are sent dry, along with the REMU-F-12 form and brief clinical summary, to the Entomology laboratory of the Institute of Diagnosis and Epidemiological Reference (InDRE), considering the indications in the "Manual for the Sending and Receiving of Samples for Diagnosis;" as well as the acceptance or rejection criteria for samples preserved dry established in the "Guidelines for Entomological Surveillance"

CONCLUSIONS

Human myiasis is more common among rural residents, especially in areas and seasons with a high density of C. hominivorax flies. The reproduction of these flies is closely linked to the presence of warm-blooded animals. Therefore, an increase in cases of animal myiasis may lead to an increase in human cases. Considering the transmission mechanism of C. hominivorax, it is essential to monitor mobile people and their pets, as they may have inadequately treated wounds during their travels. Timely examination and care of these lesions is essential to prevent introduction via this route.

...

**Pathfinder** · May 13, 2025, 10:04 AM

Mexico - New world screwworm (Cochliomyia hominivorax) - Immediate notification
...
REPORT DATE
2025/05/09
...
EPIDEMIOLOGICAL COMMENTS

An outbreak of myiasis was reported in the State of Veracruz in cattle. The lesion of the affected animal was treated with negasunt 3% (coumaphos and propoxur) to eliminate Cochliomyia hominivorax larvae. Ivermectin 1% was applied parenterally and all animals were sprayed with cypermethrin and chlorpyrifos.
...

Announcement

Mexico - New World Screwworm (NWS) outbreak 2025-2026

Mexico - New World Screwworm (NWS) outbreak 2025-2026

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