The biology of parasites from the genus Argulus and a review of the interactions with its host
G. F. Wiegertjes, G. Flik in Host-Parasite Interactions, 2004
Section 2 discussed the life cycle of these parasites and drew attention to the fact that these animals can and frequently do leave their hosts for a variety of reasons (e.g. accidental dislodging, mate location, egg deposition, new host location). During these ‘off-host’ periods argulids must propel themselves through the water column with a great deal of efficiency, especially if they are aiming to successfully locate a new host. Indeed, argulids are quite proficient swimmers. Propulsion is provided in the main by the four pairs of thoracopods located on the posterior portion of the animal’s ventral surface. These appendages exhibit the primitive crustacean form (Martin, 1932) in that they are cirriform and biramous with two segmented sympods and rami each with lateral rows of pinnate setae (Benz and Otting, 1996). The long setae found on these swimming appendages form a paddle-like surface as they beat backwards, propelling the animal forwards. These limbs are also frequently moved backwards and forwards whilst the louse is attached to its host, presumably to provide a continual flow of fresh water across the respiratory areas. In addition argulids can also ‘catapult’ themselves very quickly over a short distance using a method similar to that employed by lobsters and shrimps. The lice rapidly flick their abdominal lobes ventrally and towards the anterior of their bodies at the same time as flexing the whole carapace. This action is typically used in predator avoidance although it is possible that lice will also use the same technique to ‘jump’ onto a passing fish.
Mites
Gail Miriam Moraru, Jerome Goddard in The Goddard Guide to Arthropods of Medical Importance, Seventh Edition, 2019
Ornithonyssus sylviarum also is similar in appearance to the tropical rat mite but has a much shorter sternal plate (Figure 24.10). This plate has only four setae; the setae on the dorsal plate are quite short. The northern fowl mite is a pest of domestic fowl, pigeons, sparrows, and starlings. The species overwinters in bird nests or cracks and crevices of buildings. Unlike the chicken mite, Dermanyssus gallinae, the northern fowl mite spends its entire life on the host. In poultry houses, the mites are usually only found on the birds, but they have been found on eggs and cage litter. Northern fowl mites cannot survive more than a month or so in the absence of their poultry hosts. The northern fowl mite occurs in temperate regions worldwide.
Anal fistula
P Ronan O’Connell, Robert D Madoff, Stanley M Goldberg, Michael J Solomon, Norman S Williams in Operative Surgery of the Colon, Rectum and Anus Operative Surgery of the Colon, Rectum and Anus, 2015
The term ‘seton’ is derived from the latin word ‘seta’, meaning a bristle. Setons are used in fistula surgery in various ways. They are classified as loose or cutting (tight, snug, or chemical) according to their different properties and modes of action. The loose seton can be used for different reasons in the management of anal fistulae. A loosely tied thread can be used to drain sepsis and to allow subsidence of acute inflammation, as a drain for the primary track following eradication of secondary extensions before subsequent definitive surgery, or as a long-term palliative measure aimed at symptom control (by preventing the fistula track from occluding, and allowing sepsis to drain, thereby avoiding recurrent abscess formation and covert spread of sepsis). It can also be used as a marker to help determine the amount of muscle enclosed by the fistula, perhaps because scarring from previous surgery or relaxation under anesthesia makes assessment during surgery difficult. In such circumstances, the proportion of enclosed sphincter above and below the fistula may be more accurately determined when the patient is awake and the track marked by the seton.
Human exposure to larvae of processionary moths in France: study of symptomatic cases registered by the French poison control centres between 2012 and 2019
Published in Clinical Toxicology, 2022
Pauline Vasseur, Sandra Sinno-Tellier, Jérôme Rousselet, Jérôme Langrand, Alain Roques, Juliette Bloch, Magali Labadie
People can be exposed to urticating larvae of pine processionary moth from January to May and to those of oak processionary moth from April to July. Both larvae are characterized by a rather similar venomous stinging device that is considered to represent a defense against their vertebrate predators [1]. Microscopic-sized urticating setae (40–400 microns) with a sharp spicule shape are inserted next to each other in articulated structures regularly placed on the backbone of the larva, and where glands produce urticating proteins that would be released when the seta breaks [11]. Broken setae of pine processionary larvae release several substances, including thaumetopoein [12] while those of oak processionary larvae release a thaumetopoein-like protein. The pathophysiological mechanism for urticating setae involves allergic and non-allergic components. Immediate reactions may occur by mast cell degranulation while IgE-mediated sensitization may occur in the event of repeated exposure [13]. When disturbed, processionary larvae actively release their setae into the atmosphere. Wind and ambient currents can easily disperse the setae that can crash into the skin and the mucous membranes (eyes, nose, mouth…), break and release urticating proteins.
A Hairy Affair: Ophthalmia nodosa Due to Caterpillar Hairs
Published in Ocular Immunology and Inflammation, 2018
Pratik Y. Doshi, Ugam Usgaonkar, Pradnya Kamat
In total, 52 species of moths spanning 10 families of Lepidoptera are known to cause urticaria; there are, however, only six varieties known to cause ophthalmia nodosa.12 Contact with caterpillar setae can be through direct contact with caterpillars, contact with the larval cocoon into which setae may have been shed, and interwoven or direct entry of wind-borne setae.8 The problems caused by the setae are related to their toxicity and locomotion. Toxicity is due to the presence of a foreign body and the effect of released urticating toxins. Toxin originates in the venom gland connected to the hair shaft, which is transferred via the hollow shaft seen in the electron micrographs.13 The resultant inflammation in the conjunctival and episcleral tissues would give rise to the classical protruding nodules. However, the stiffer cornea and sclera do not expand to permit any such nodule formation. Histopathology of the lesions shows typical granulomatous reaction to a chemical irritant. The hairs are surrounded by lymphoid cells, macrophages, and epitheloid cells; surrounded by a thick fibrous capsule, hence the name ophthalmia nodosa.
Effect of Tagetes minuta oil on larval morphology of Plutella xylostella through scanning electron microscopy and mechanism of action by enzyme assay
Published in Toxin Reviews, 2022
Shudh Kirti Dolma, C. S. Jayaram, Nandita Chauhan, S. G. Eswara Reddy
Setae on the whole habitus differentiated based on the chaetotaxy proposed by Moriuti (1977). Larva treated with T. minuta oil was shrunken and dissolved, so unable to identify the setae on the head, thorax, and abdomen but deformed setae observed on the whole habitus at different intervals over the time (Figure 2(a–d)). At 24 h of treatment, seta initiated to modify both from the tip and base like clubbed and globose, respectively (Figure 2(a)) as compared to untreated control (Figure 2(h)) but the tip started broken after 48 h (Figure 2(b)). Clubbed part of the setae swollen to the higher extent and shaft of the hair broken, left with broken bloated seta after 72 h. Ultimately, hair socket fragmented the bloated setae after 96 h. Setae near the various parts of the larva also recorded the similar structural modifications in the vicinity of stemmata, posterior abdominal segments (10th and 11th), and ventral part of the mouthparts (Figure 2(e–g)).
Related Knowledge Centers
- Chitin
- Integument
- Mechanoreceptor
- Mycology
- Parasitism
- Peristalsis
- Bristle
- Hair
- Bristle Sensilla
- Process