Giardia Colonizes and Encysts in High-Density Foci in the Murine Small Intestine

ABSTRACT Giardia is a single-celled parasite causing significant diarrheal disease in several hundred million people worldwide. Due to limited access to the site of infection in the gastrointestinal tract, our understanding of the dynamics of Giardia infections in the host has remained limited and largely inferred from laboratory culture. To better understand Giardia physiology and colonization in the host, we developed imaging methods to quantify Giardia expressing bioluminescent physiological reporters in two relevant animal models. We discovered that parasites primarily colonize and encyst in the proximal small intestine in discrete, high-density foci. We also show that high parasite density contributes to encystation initiation. Giardia lamblia is a highly prevalent yet understudied protistan parasite causing significant diarrheal disease worldwide. Hosts ingest Giardia cysts from contaminated sources. In the gastrointestinal tract, cysts excyst to become motile trophozoites, colonizing and attaching to the gut epithelium. Trophozoites later differentiate into infectious cysts that are excreted and contaminate the environment. Due to the limited accessibility of the gut, the temporospatial dynamics of giardiasis in the host are largely inferred from laboratory culture and thus may not mirror Giardia physiology in the host. Here, we have developed bioluminescent imaging (BLI) to directly interrogate and quantify the in vivo temporospatial dynamics of Giardia infection, thereby providing an improved murine model to evaluate anti-Giardia drugs. Using BLI, we determined that parasites primarily colonize the proximal small intestine nonuniformly in high-density foci. By imaging encystation-specific bioreporters, we show that encystation initiates shortly after inoculation and continues throughout the duration of infection. Encystation also initiates in high-density foci in the proximal small intestine, and high density contributes to the initiation of encystation in laboratory culture. We suggest that these high-density in vivo foci of colonizing and encysting Giardia likely result in localized disruption to the epithelium. This more accurate visualization of giardiasis redefines the dynamics of the in vivo Giardia life cycle, paving the way for future mechanistic studies of density-dependent parasitic processes in the host. IMPORTANCE Giardia is a single-celled parasite causing significant diarrheal disease in several hundred million people worldwide. Due to limited access to the site of infection in the gastrointestinal tract, our understanding of the dynamics of Giardia infections in the host has remained limited and largely inferred from laboratory culture. To better understand Giardia physiology and colonization in the host, we developed imaging methods to quantify Giardia expressing bioluminescent physiological reporters in two relevant animal models. We discovered that parasites primarily colonize and encyst in the proximal small intestine in discrete, high-density foci. We also show that high parasite density contributes to encystation initiation.

HUBUNGAN STATUS GIZI DENGAN TINGKAT KEPADATAN PARASIT MALARIA PADA ANAK

Latar belakang: Status gizi diketahui dapat mempengaruhi kepadatan parasit malaria pada anak, sehingga melalui status gizi dapat dinilai tingkat kepadatan parasit malaria. Namun status gizi bukan merupakan satu-satunya faktor yang menyebabkan tingginya kepadatan parasit malaria, terdapat faktor lain yang turut berperan dalam hal ini. Tujuan: Untuk mengetahui hubungan antara status gizi dengan tingkat kepadatan parasit malaria. Metode: Penelitian ini menggunakan metode penelitian analititik retrospektif dengan pendekatan potong lintang (cross sectional). Sampel penelitian sebanyak 59 anak yang memenuhi kriteria inklusi. Data dianalisis menggunakan uji koefisien korelasi Gamma. Hasil: Dari 65 anak didapatkan 59 sebagai sampel penelitian yang memnuhi kriteria inklusi. Status gizi dengan kepadatan parasit malaria didapatkan kepadatan tinggi dengan gizi kurang sebanyak 9 anak (15,3%), dengan gizi baik sebanyak 24 anak (40,7%), dengan overweight sebanyak 2 anak (3,4%) dan dengan obesitas sebanyak 2 anak (3,4%). Sedangkan kepadatan rendah dengan gizi kurang sebanyak 9 anak (8,5%), dengan gizi baik sebanyak 13 anak (22,0%), dengan overweight sebanyak 3 anak (5,1%). Dengan uji koefisien korelasi Gamma didapatkan korelasi yang sangat lemah (rG = 0,118; p = 0,632). Hasil ini menyatakan bahwa tidak terdapat hubungan yang bermakna antara status gizi dengan kepadatan parasit malaria.Kesimpulan: Tidak terdapat hubungan yang bermakna antara status gizi dengan tingkat kepadatan parasit malaria pada anak.Kata kunci: Malaria, kepadatan parasit, status gizi, anak.Background: Nutritional status can influence malaria parasite density in children, so from nutritional status we can evaluate malaria parasite density. Nutritional status is not the only factor which cause high malaria parasite density, there are another factors which cause this. Objective: To find out the relation between nutritional status and malaria parasite density in children. Methods: This study uses analytic retrospective method with cross –sectional design. About 59 sample qualify the inclusion criteria. Data were analyzed using Gamma correlation coefficient statistical test. Results: From 65 children, there are 59 children who qualify the inclusion criteria. On the analysis of nutritional status and malaria parasite density, children with high parasite density consist of 9 children (15,3%) with malnutrition, 24 children (40,7%) with good nutritional status, 2 children (3,4%) with overweight, and 2 children (3,4%) with obesity. On children with low parasite density, there are 9 children (8,5%) with malnutrition, 13 children (22,0%) with good nutritional status, and 3 children (5,1%) with overweight. Using Gamma correlation test, the study find a very weak correlation (rG = 0,118; p = 0,632). This find indicates that there is no significant relation between nutritional status and malaria parasite density. Conclusion: There is no significant relation between nutritional status and malaria parasite density in children.Keywords: Malaria, parasite density, nutritional status, children.

Evidence for both innate and acquired mechanisms of protection from Plasmodium falciparum in children with sickle cell trait

Sickle cell trait (HbAS) is known to be protective against Plasmodium falciparum malaria, but it is unclear when during the course of infection this protection occurs and whether protection is innate or acquired. To address these questions, a cohort of 601 children 1-10 years of age were enrolled in Kampala, Uganda, and followed for 18 months for symptomatic malaria and asymptomatic parasitemia. Genotyping was used to detect and follow individual parasite clones longitudinally within subjects. Children with HbAS were protected against the establishment of parasitemia, as assessed by the molecular force of infection at older but not younger ages (at 2 years of age: incidence rate ratio [IRR] = 1.16; 95% confidence interval [95% CI], 0.62-2.19; P = .6; at 9 years of age: IRR = 0.50; 95% CI, 0.28-0.87; P = .01), suggesting an acquired mechanism of protection. Once parasitemic, children with HbAS were less likely to progress to symptomatic malaria, with protection again being the most pronounced at older ages (at 2 years of age: relative risk [RR] = 0.92; 95% CI, 0.77-1.10; P = .3; at 9 years of age: RR = 0.68; 95% CI, 0.51-0.91; P = .008). Conversely, the youngest children were best protected against high parasite density (at 2 years of age: relative density = 0.24; 95% CI, 0.10-0.54; P = .001; at 9 years of age: relative density = 0.59; 95% CI, 0.30-1.19; P = .14), suggesting an innate mechanism of protection against this end point.

Life cycle of Babesia argentina (Lignières, 1903) (Sporozoa : Piroplasmidea) in the tick vector Boophilus microplus (Canestrini)

Babesia argeutina, a protozoan parasite causing tick fever of cattle in Australia, is transmitted by Boophilus microplus. Its development in this invertebrate vector is very similar to that recorded by Riek (1964) for Babesia bigemina. Many of the parasites occurring in the bovine erythrocytes are destroyed on ingestion but the early development in the lumen of the gut is uncertain. By about 36 hr, blunt, cigar-shaped forms, 7.2–1 3.8 µ by 2.6–5.6 µ, invade the epithelial cells of the gut and subsequent development is by means of multiple fission. This leads, by about 96 hr, to the production of mature vermicules which measure about 15.8 µ by 3.0 µ, with a range of 14.3–16.9 µ by 2.8–3.5 µ. At about this time vermicules enter the mature ova of the tick, and a further cycle of multiple fission in the gut cells of the developing larva gives rise to vermicules similar to those produced in the adult tick. The final cycle takes place in the salivary glands of the larva, and the forms infective to the vertebrate host appear 2–3 days and longer after larval attachment. Multiplication in this cycle is also by multiple fission and gives rise to comparatively small numbers of infective forms measuring about 1.5 µ by 1.0 µ. Not all ticks develop an infection even after engorging on blood with a high parasite density. Certain 'strains' of Boophilus microplus seem to be more susceptible to infection than others. Heavy mortalities occurred in many ticks after ingesting blood with a parasite density of 5% or higher.